The tunnel will be approximately 12,500ft (3,840m) long, 23ft (7m) in diameter, and supported by a bolted, gasketed, one-pass lining system. The work will include six 90ft to 100ft (30m) deep shafts ranging from 12ft (3.6m) to 75ft (23m) in diameter. Three Adit connections are also required between the tunnel and three of the shafts; these adits will be between 4ft (1.2m) and 10ft (3m) in diameter.
"This decision by the Board of Directors sets in motion a very significant portion of the Clean Rivers Project," said DC Water board chairman Allen Y. Lew. "This metro-sized tunnel will store combined-sewer runoff during intense rainstorms to prevent CSOs to the Anacostia River, improving the health of this important District waterway."
