The new tunnel will not replace the old tunnels, but it will allow for improvements of the water supply system as it will allow DEP to shut down and repair the old tunnels for the first time in history, Timbers says.

Water that will flow through Tunnel No. 3 will originate from New York state's Catskill/Delaware watersheds. The water will be disinfected at DEP's ultaviolet (UV) filtration facility in Mount Pleasant and Greenburgh, N.Y., which was completed in January. The 160,000-sq-ft facility, which can treat 2 billion gallons a day and uses gravity instead of pumps to convey water through the system, is the largest UV water treatment facility nationwide.