Project Description

The South Cobb Tunnel is the largest capital improvement project in Water System history. A $305,000,000 construction contract was awarded to Shea –Traylor J.V. (a joint venture of J.F. Shea Construction and Traylor Brothers) on March 11, 2008. Construction began in July 2008 and will take six years to complete.

This project will provide needed long-term sewer conveyance capacity and equalization for the Sweetwater Creek and Nickajack Creek basins located in western and southern Cobb County, and will allow Cobb to eliminate two major pumping stations and about 87,000 linear feet of aging sewer line and force main.

The South Cobb Tunnel project entails constructing a six mile, 27-foot excavated diameter tunnel located in hard rock, with depths ranging from 150 feet to 400 feet. Most of this main tunnel will be excavated using a 27-foot tunnel boring machine (TBM). Several six-foot diameter tunnels and one ten-foot diameter tunnel with lengths ranging from 100 to 3,200 linear feet will be constructed also.

The main tunnel alignment will begin near the intersection of Maxham Road and Old Alabama Road continue southeast along the county line then turn east just north of 1-20 and continue east to the South Cobb WRF. To view a map of the project click here.

The project also includes building a deep lift station with a capacity of 130 million gallons per day at the South Cobb Water Reclamation Facility (WRF) to convey waste water flows from the tunnel to the plant for treatment. The Water System completed the Chattahoochee Tunnel, a six and a half mile tunnel with an excavated diameter of 18 feet, in 2004. The Chattahoochee Tunnel project was very successful and has been operating as expected. The Water System fully anticipates a similar level of success on the South Cobb Tunnel project.