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Fixing a Very Big Leak

I almost missed this pretty amazing article in the Sunday NY Times, buried (no pun intended) in the National/New York section of my New England edition. It describes, among other things, the work being done by a team of commercial deep-sea divers to repair and evaluate damage on a section of the Rondout-West Branch tunnel, which carries water from Catskill reservoirs to New York City. It’s been leaking for decades — around 20 million gallons a day — but recently the losses on bad day amount to nearly twice that, and as a result the upstate village of Wawarsing, which sits above the pipline, claims that it is being flooded from below.

Now, the divers: While the water in the 13.5-foot-wide tunnel isn’t deep, the section where they are working to repair a giant valve is at the bottom of a 700-foot below-ground shaft, making this a sort of virtual deep dive that requires the divers to endure some pretty extreme working conditions. From the story:

“[The divers] are living for more than a month in a sealed 24-foot tubular pressurized tank complete with showers, a television and a Nerf basketball hoop, breathing air that is 97.5 percent helium and 2.5 percent oxygen, so their high-pitched squeals are all but unintelligible. They leave the tank only to transfer to a diving bell that is lowered 70 stories into the earth, where they work 12-hour shifts, with each man taking a four-hour turn hacking away at concrete to expose the valve.”

Once the valve is working, it is hoped, the tunnel can be drained and necessary patches made. This is just one part of a huge infrastructure project to repair the city’s water delivery systems. A major component of this renewal effort, “New York City Water Tunnel No. 3,” was started nearly 40 years ago and isn’t schedule for completion until 2015.

The stuff about the divers reminded me of an amazing book of nonfiction I read a couple of years ago called Shadow Divers, a real-life deep-sea wreck-diving adventure that goes into more detail than you think ever wanted to know about the technical aspects of deep dives. Truly fascinating, and a page-turner. From my limited reading on deep diving, though, I have serious doubts about the accuracy of one fact in the Times story — that the divers are breathing air containing less than 3% oxygen. Ten percent or so is what I would expect. If correct, this is extreme diving indeed.

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