Faster Travel Time Around Atlanta

Faster Travel Time Around Atlanta


I-75 South Metro Express Lanes
Reinforced Earth Product in Field
Location: 
Atlanta, GA
Owner: 
Georgia Department of Transportation
Contractor: 
C.W. Matthews Contracting Co. Inc.
Subcontractor: 
Bonn-J Contracting Inc.
Engineer: 
United Consulting

To provide access to and from both travel directions of the adjacent mainline roadways, managed lanes are often constructed in the highway median. In this sometimes narrow space, Mechanically Stabilized Earth (MSE) retaining walls can efficiently retain grade differences across the median between the flanking mainline roadways, supporting ramps, and bridge abutments that are typical of reversible lanes.

An example of this can be seen on Georgia DOT’s I-75 South Metro project, one of several express lanes projects currently in the Atlanta area. The I-75 South Metro Express Lanes project extends twelve miles along I-75 from McDonough Road to Stockbridge Highway, and is planned for completion in early 2017. The project will provide variable priced toll lanes that are reversible based on the peak periods of traffic flow.

To expedite the project while optimizing design and reducing costs, GDOT is using the design-build project delivery method. Experienced road builder C.W. Matthews Contracting Co., Inc. teamed with design engineer Arcadis, geotechnical engineer United Consulting, and MSE wall erection subcontractor Bonn-J. The Reinforced Earth Company (RECo) was selected to provide the 18 required MSE wall structures totaling nearly 98,000 square feet of facing, which is an area equivalent to almost two football fields.

Two of the 18 Reinforced Earth® MSE walls on this project had unique design requirements:

• The geotechnical report for one wall suggested the possibility of settlement. The wall was constructed up to the top panels, then a 30-day minimum waiting period was required by the geotechnical engineer. After confirming the settlement was complete, the traffic barrier was cast on the top of the wall, and final grading and paving was completed.

• In another case, the benefits of the design-build approach were demonstrated. One MSE wall was was originally designed so that the reinforcing strips would have to extend to the edge of the existing southbound I-75 travel lane. This would have required a significant expense for a shored excavation with a traffic detour. To address the problem, the contractor’s team worked with RECo’s engineers to relocate and redesign the wall, eliminating the need for shoring and a detour.

Matthews’ and Bonn-J’s extensive experience working with RECo’s wall systems provided another significant benefit - to field operations. Since all of the walls are immediately adjacent to I-75, the job site had very limited "laydown" area for storing concrete wall panels, steel reinforcing strips, and other materials needed for installation. Because maintaining a high production rate is crucial to both project flow and efficiency, the contractors carefully coordinated the deliveries of wall materials so as to always have only what was needed available on site.

As Georgia DOT continues to implement a new system of express lanes across the region, RECo is excited to play a role in the improvement in the daily transportation of the citizens of the Atlanta area, including members of our own team in Norcross and Newnan, GA.