The New York Times summarizes the event: After Decades, a Water Tunnel Can Now Serve All of Manhattan:
In one of the most significant milestones for the city’s water supply in nearly a century, the tunnel — authorized in 1954, begun in 1970 and considered the largest capital construction project ever undertaken in the five boroughs — will for the first time be equipped to provide water for all of Manhattan. Since 1917, the borough has relied on Tunnel No. 1, which was never inspected or significantly repaired after its opening.
The New Yorker celebrates the event by re-visiting their 10-year-old article on the life of the "sandhogs": Building Water Tunnel No. 3:
The old tunnels, Ryan explained, were leaking “like a sieve”; some of the sections were built nearly a century ago and were in desperate need of repair. But until Tunnel No. 3 is virtually complete there will be no way to fix them. In part, this is because getting inside Tunnel No. 1 or No. 2 would require the city to shut the water off, and without a backup supply there would be serious water shortages. But it was more than that, and, as several sandhogs peered over his shoulder, Ryan started to draw a circle on the table with his muddy finger. “See this?” he asked me. “These are the valves that control the flow of water.”
“They’re hundreds of feet underground,” another sandhog said.
The valves were designed, Ryan said, to open and close guillotine-like gates inside the cylindrical tunnels, stopping the flow of water. But they had become so brittle with age that they were no longer operable. “They’re afraid if they try to shut the valves they won’t be able to turn ’em back on,” Ryan said.
PBS classifies Water Tunnel Number 3 as one of the "Wonders of the World": Building Big: Databank: New York Third Water Tunnel, highlighting one of the least boring machines in the world, the High Performance Tunnel Boring Machine for Queens Water Tunnel, No. 3:
The Robbins HP open hard rock TBM, as shown in Figure 2., weighs 610 metric tons (1,345,000 lb) approximately and has a diameter of 7.06 m (23 ft 0 in). The machine can be modified to any diameter between 6.50 m (21 ft 4 in) and 8.50 m (27 ft 11 in), making it suitable for future hard rock tunneling projects. The TBM consists of three major components, the Cutterhead/Cutterhead support, Gripper, and Main Beam assemblies.
And since pictures are the best, here's some from The Verge, but definitely don't miss Geoff Manaugh's super photo essay in Gizmodo: In An Artificial Cave 200' Beneath Central Park with Michael Bloomberg.
And, everywhere we looked, there were other levels, or hydra-like piped connections leading onward to spaces we could see or infer, but never physically enter.
On the floor of the press room itself, for example, there was a manhole, promising further systems and drains far below ...
... and the walkways of the central room itself were steel grates that felt less like a floor in any real, architectural sense and more like an arbitrary level simply plonked down in the room wherever the engineering allowed for it, just a viewing platform for inspecting the bits and bobs of machinery poking out from beneath.
Welcome to the world, City Water Tunnel No. 3!