Installed in 1911, the flushing tunnel is a large propeller that brings water into the Gowanus Canal from Buttermilk Channel (between lower Brooklyn and Governor’s Island through a brick-lined 1.2-mile (1.9-km) tunnel. Rehab of the tunnel began in 1994 and it was then reactivated in 1999. An upgrade began in 2010 and it was once again reactivated in 2014.