Mission Complete: DC Water’s First Tunnel Boring Machine Finishes 7.2-km Tunnel

September 15, 2015

Featured, Multimedia

Lady Bird’s cutterhead, the elaborate steel face of the machine with built-in cutting and slicing tools, is lifted from a 100-ft (30-m)-deep shaft. Photo courtesy of Ted Coyle, DC Water.

Lady Bird’s cutterhead, the elaborate steel face of the machine with built-in cutting and slicing tools, is lifted from a 100-ft (30-m)-deep shaft. Photo courtesy of Ted Coyle, DC Water.

Lady Bird, DC Water’s (Washington, D.C.) tunnel boring machine (TBM), has completed a 7.2-km (4.5-mi) tunnel that will be used to help improve water quality in the Anacostia River. In July, Lady Bird completed the dig, and its cutterhead — the elaborate steel face of the machine with built-in cutting and slicing tools — was extracted from a 100-ft (30-m)-deep shaft near DC Water’s Main Pumping Station, according to a DC Water news release.

Lady Bird’s journey began in July 2013 at the Blue Plains Advanced Wastewater Treatment Plant. Since then, it has removed approximately 1.2 million tons of material from underground. This material has been hauled away in nearly 72,000 truckloads during 2 years. The tunnel has been built with 28,189 precast concrete segments forming 4027 full rings, the news release says.

To prepare for TBM’s arrival at the pumping station, the shaft was filled with flowable fill concrete and water to protect from changes in pressure as Lady Bird mined through the shaft wall. Crews then dug out the concrete to reveal the machine. A heavy-duty crane was deployed to hoist the cutterhead and the other pieces of TBM, the news release says.

With the DC Water Main Pumping Station in the background, Lady Bird emerges from its tunnel boring mission. Photo courtesy of Ted Coyle, DC Water.

With the DC Water Main Pumping Station in the background, Lady Bird emerges from its tunnel boring mission. Photo courtesy of Ted Coyle, DC Water.

“This is a terrific milestone for DC Water’s Clean Rivers Project,” said DC Water CEO and General Manager George S. Hawkins. “We are fortunate that the tunneling went so smoothly, finishing on time and on budget.” Hawkins recognized DC Water staff, the company, Dee Traylor/Skanska/Jay Joint Venture (Washington, D.C.), and others for their efforts in the “successful dig.”

DC Water’s Clean Rivers Project will incorporate two methods to keep wastewater and stormwater from overflowing into waterways during heavy rains. The first method is to build underground tunnels that will hold combined wastewater and stormwater until rain subsides, then convey it to Blue Plains for treatment. The second method is to create green infrastructure to capture and infiltrate rain onsite before it can reach the combined sewer system.

See videos of Lady Bird and the Clean Rivers Project at

—  LaShell Stratton-Childers, WEF Highlights

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