The Robbins Main Beam TBM, dubbed “Driller Mike”, was launched on Atlanta, Georgia, USA’s Bellwood Tunnel in October 2016.
The Robbins Main Beam TBM, dubbed “Driller Mike”, was launched on Atlanta, Georgia, USA’s Bellwood Tunnel in October 2016.
The 3.8 m (12.5 ft) diameter Robbins Main Beam TBM will bore the 8.0 km (5.0 mi) Bellwood Tunnel through granite rock with potential zones of water inflows.
The 3.8 m (12.5 ft) diameter Robbins Main Beam TBM will bore the 8.0 km (5.0 mi) Bellwood Tunnel through granite rock with potential zones of water inflows.

A 12.5-foot-diameter tunnel boring machine (TBM) dubbed “Driller Mike” is boring a 5-mile emergency water supply tunnel for the City of Atlanta’s Department of Watershed Management.

Right now, downtown Atlanta has enough water to last three days. Running from an inactive quarry and under a treatment plant and reservoir before ending next to the Chattahoochee River, the Bellwood Tunnel will make sure supplies last from 30 days to 90 days.

“If the city were to lose water supply for a day, the economic impact would be at least $100 million per day," says Bob Huie Sr., project manager for the construction manager at risk, PC/Russell JV. "Spending $300 million on this project seems a pretty good investment in comparison to what could happen."

Excavation is scheduled to be completed in the first quarter of 2018. After final lining, the tunnel will be filled with water and the quarry site will become Atlanta’s largest reservoir and park, totaling hundreds of acres. While the park site is a bonus for residents, the water storage capacity it will provide is critical. Nearly 1.2 million customers, including 200,000 passengers who pass through the world’s busiest airport every day, count on that water supply every time they turn on the tap.

The tunneling machine is excavating in granite, with at least 1,000 feet of zones in three separate areas that will require continuous probing. In a section directly below the reservoir, monitoring will be particularly crucial to ensure no water inflows occur. The machine must also negotiate several curves.

“We have one curve in the first 1,000 feet and the main 1,200-foot-radius curve is 6,000 feet in," says Larry Weslowski, tunneling superintendent for the PC/Russell JV. "We plan to do short strokes -- about 8 inches to a foot shorter than normal -- in this section to get through the curves.”

The PC/Russell JV sub-contracted with the Atkinson/Technique JV to operate the machine and will oversee construction of various intake and pumping shafts as well as final lining operations.