A $192 million contract for reconstruction of the I-20 and I-520 Interchange in Augusta, Ga., was awarded in April 2007 to a joint venture of Scott Bridge Company Inc., Opelika, Ala., and United Contractors, Great Falls, S.C. by the Georgia Department of Transportation (GDOT). Work began in June 2007 and should take approximately three years to complete.
The project includes widening 6.25 mi. (10 km) of additional lanes along I-20 and adding collector-distributor lanes along eastbound and westbound I-520 and eastbound I-20. Reconstruction of the I-20/I-520 interchange also is planned and will consist of adding two flyover ramps and three grade-separated interchanges, including one at Scott Nixon Memorial Parkway and I-520. In addition, I-20 will be widened from Belair Road to Wheeler Road in Columbia and Richmond counties.
Scott Bridge is building three of the structures, United Contractors is building one, and the other is subbed out. In addition to the prime contractors, there are roughly 30 subcontractors on the project performing various duties.
A range of walls are being installed as part of the contract. Sam Stutt, project manager of United Contractors said that since the project site is so tight and compact, walls are needed for many reasons, including keeping dirt in place. Concrete walls, MSE walls, and sound barrier walls are all being installed and have their own functions.
“Any Federal Aid project requires sound barrier walls,” stated Stutt, “whenever there is residential [area near the project].”
A unique part of the contract involves the construction of the storm water retention ponds, many inside the interchange’s loops. There are 10 total ponds and “not all necessarily inside loops,” said Stutt. The interchange is in a flood prone area, so the design of the project includes water retention features that will help stop flooding.
The collector-distributor lanes have become more popular as a replacement to the traditional cloverleaf interchange design. Stutt called the cloverleaf design “dangerous” for motorists trying to merge onto or off of the interstate. Instead, collector-distributor lanes allow drivers to ride parallel to the interstate while exiting and entering the highway. The lanes travel one-way and are intended to move or eliminate weaving from the main lanes of the interstate highway, particularly at the cloverleaf interchanges.
One challenging aspect of the project is the rigid work zone that the contractors are faced with.
“All this expansion is occurring in the original footprint of the original interstate system,” explained Stutt. As a result, the project requires little addition of right-of-way but also doesn’t leave much room for staging equipment.
Greenhorne & O’Mara, Consulting Engineers, headquartered in Laurel, Md., provided complete design services for the I-20/I-520 interchange reconstruction, including the I-20 widening and the reduction of peak flows of Crane’s Creek.
Stutt described the equipment that is being used as “run of the mill” and not specialized. At one point, he said, there were an impressive “10 crane booms in the air,” which included a 150-ton (136 t) Kobelco 1600 and a 150-ton Manitowoc. Cat equipment also is on site as well as CMI pavers.
The project is “75 percent to 80 percent complete,” Stutt said. One last flyover deck needs to be poured. Of the grade-separation bridges, one has a third left to complete while another is halfway finished. Concrete pavement sections are halfway complete and asphalt pavement is three-quarters finished. Contractors will be using a total of 250,000 sq. yd. (200,000 sq m) of asphalt and 250,000 sq. yd. of concrete. All walls included in the contract have been finished.
In the end, the improvements to the interchange will be manifold. Improvements include replacing the existing interchange configuration, increasing the capacity of the interchange, separating local trips from through traffic and reducing noise pollution. Also, the increased storm water retention will reduce discharges into Crane’s Creek Drainage Basin. Lastly, the design will provide a more sophisticated and clean urban aesthetic.
Interstate 520, also known as the Bobby Jones Expressway, forms a loop around the western and southern portions of the Augusta metropolitan area. The original completion date for the I-20/I-520 project was set for July 31, 2010, but the contractors plan on an early delivery of Oct. 31, 2009.