All tunnels leak, but this one is a sieve. For most of the last two decades, the Rondout-West Branch tunnel — 45 miles long, 13.5 feet wide, up to 1,200 feet below ground and responsible for ferrying half of New York City’s water supply from reservoirs in the Catskill Mountains — has been leaking some 20 million gallons a day. Except recently, when on some days it has lost up to 36 million gallons.
After tiptoeing around the problem for many years, and amid mounting complaints of flooded homes in the Ulster County hamlet of Wawarsing, the city’s Department of Environmental Protection has embarked on a five-year, $240 million project to prepare to fix the tunnel — which includes figuring out how to keep water flowing through New Yorkers’ faucets during the repairs. The most immediate tasks are to fix a valve at the bottom of a 700-foot shaft in Dutchess County so pumps will eventually be able to drain the tunnel, and to ensure that the tunnel does not crack or collapse while it is empty.