|Jan 05, 2017 -- Today, DC Water and its contractors lifted the face of the latest massive tunnel boring machine (TBM), Nannie, from a depth of 102 feet to the surface. The nearly 90-ton cutterhead required a special crane counterbalanced with more than 150 ton weights. The cutterhead is equipped with a system of scrapers that bore through the earth, with the football-field-long tunnel boring machine and trailing gear following behind. In mining culture, the lifting of the cutterhead is a ceremonial mark of the end of the tunnel boring machine’s journey.
Nannie began her journey in November 2015, starting at RFK Stadium, tunneling south to Poplar Point for more than two miles. She connected to the tunnel segment mined by her sister TBM, Lady Bird, that ends at DC Water’s Blue Plains Advanced Wastewater Treatment Plant.
These two tunnel segments are slated to be operational in early 2018, bringing relief from combined sewer overflows to those portions of the Anacostia and Potomac Rivers.