Lady Bird, Traylor’s Herrenknecht TBM, has completed her mission, mining a four-and-a-half-mile-long tunnel for DC Water’s combined sewer overflow tunnel. She completed her dig earlier this month, and on July 23rd her cutterhead was extracted from the 100-foot-deep Main Pumping Station shaft.
Lady Bird began her journey two years ago, in July of 2013, from a deep shaft excavated at the Blue Plains Advanced Wastewater Treatment Plant. She tunneled along the Potomac River northward to Poplar Point, crossed under the Anacostia River and continued west, finishing at a deep shaft along Tingey Street, SE. The shaft was filled with flowable fill concrete and water to protect against changes in pressure as Lady Bird mined through the shaft wall. Crews then dug out the concrete to reveal the now muck-brown machine. A special heavy-duty crane was deployed to hoist the cutterhead and other TBM parts too heavy for the cranes already on site.
Lady Bird removed approximately 1.2 million tons of material, which was hauled away in nearly 72,000 truckloads over the last two years, and set 28,189 precast concrete segments for a total of 4,027 full rings.
“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, and I applaud our DC Water staff as well as Traylor Skanska Jay Dee and everyone else who took part in this successful dig.”