SFGTV2 December 29, 2012
They run hundreds of feet below manhattan, far deeper than the subways. Built at the beginning of the 20th century, they are concretelined and bored through solid rock. They could last centuries. But the mechanical equipment within them will not. Engineers in the 1950s discovered rust on the tunnels valves. There were concerns that if they closed the valves for tunnel inspections, they may never open again, leaving new york city without water. So they chose to keep them open. As a result, there ...
Source: archive.org