Construction for two new flyover bridges on U.S. 70 at the I-85 interchange in Durham, NC, began September 1999.
One flyover will provide I-85 southbound traffic access to U.S. 70 east. The other flyover will carry U.S. 70 westbound motorists over I-85 north and southbound traffic before merging onto I-85 southbound from the right rather than the left –– as was the case with the old road.
The distance for the interchange project at U.S. 70 is approximately 1.75 mi. (2.8 km). The $50 million contract for the construction of the flyovers was funded by the Federal Highway Administration, the North Carolina Department of Transportation (NCDOT) and the City of Durham, and was awarded to Granite Construction Inc.
Granite Construction Inc. is one of the largest heavy civil contractors in the United States and largest producers of sand, gravel, asphalt and other aggregate-based construction materials. The company performs a variety of infrastructure projects including the construction of roads, highways, bridges, dams, tunnels and canals.
According to Aaron Brower, NCDOT assistant resident engineer, the old section of I-85 and U.S. 70 in Durham had four lanes of traffic with narrow shoulders. Making the situation worse was the extremely old and broken pavement, which consisted of concrete with an asphalt overlay.
“In addition,” Brower said, “there was no access from the U.S. 70 west to I-85 north or access from I-85 south to U.S. 70 east without taking an offsite detour. Westbound traffic on U.S. 70 also merged onto I-85 southbound traffic from the left, which was not very safe.”
“Upon completion, both I-85 and U.S. 70 will be six lanes wide with 12-feet shoulders and longer, safer merger ramps,” he said. “The proposed pavement structure on U.S. 70 will consist of chemical sub grade stabilization and asphalt and the pavement structure on I-85 will consist of chemical sub grade stabilization and concrete.”
Granite was responsible for all grading. According to project manager Bill McGowan, 850,000 cu. yds. (650,000 cu m) of on-site excavation and borrow excavation occurred at the job site along with 130,000 cu. yds. (99,400 cu m) of rock excavation.
“The flyovers will also be constructed of structural steel and concrete,” McGowan said. “Granite Construction Company used Economy Forms Corporation (EFCO) forms for construction of the substructure on the flyovers.”
“Several utility relocation delays and a design error on the U.S. 70 west to I-85 south bridge caused some delay.” Brower said, noting some of the challenges associated with the project. “All problems have been solved though, and the bridge is now open to traffic.”
According to McGowan, continuous complications during construction created a virtual design-build atmosphere on the project.
“However,” McGowan emphasized, “most plan revisions have gone smoothly due to the cooperation between the North Carolina Department of Transportation and Granite.”
“Another key challenge on this project,” McGowan noted, “was due to its location. This project is an exceptionally complicated job due to it being a major highway upgrade at the intersection of two very busy roads. Consequently, a traffic maintenance plan that did not restrict the flow and volume of traffic was required before construction could begin. This plan, though, has extended the project duration.”
NCDOT provided erosion control devices for monitoring erosion at the job site, with on-site inspectors creating weekly erosion control reports and submitting them to the contractors so that any deficiencies could be corrected.
“There were not any wetlands destroyed or relegated on this project.” Brower said. “And, the appropriate U.S. Army Corp of Engineers permits were attained prior to any construction.
“The old road was 50 years old and designed for minimal traffic flow.” McGowan explained. “Traffic has increased extensively, making the need to gear up to modern standards imperative. By widening the highways and constructing the flyover bridges, this will be accomplished.”
“The new improved I-85 will provide a much safer and passable highway through the City of Durham,” Brower said. “Residents of Durham can expect fewer delays and safer access merging on and off I-85 and U.S. 70.”
The anticipated date of completion is the summer of 2004.