Few projects last more than 40 years, but the New York City Department of Environmental Protection�s $6 billion, 60-mi City Water Tunnel No. 3, the largest project in the city�s history, has spanned more than four decades, with one segment open, another under way and several more elements in the works as the department aims for a 2020 completion.
�Manhattan has been served by City Water Tunnel No. 1, constructed in 1917, and in order to take that tunnel down to do repairs and replace aging piping, we needed another tunnel,� says Kathryn Mallon, deputy commissioner of the DEP�s bureau of engineering, design and construction. �It provides critical reliability and redundancy.�