September 27, 2013

Behind the Book

The Tunnel Project

A quarter-century ago, Boston Harbor was infamous for being "the dirtiest harbor in America," an open sewer that became a major issue in the presidential campaign of 1988. Today, Boston can boast of having the nation's cleanest urban harbor. The key to that undisputed environmental triumph is a state-of-the-art wastewater treatment plant sitting on tiny Deer Island north of Boston, and an engineering marvel of an outfall tunnel. Every day, that nearly 10-mile-long Deer Island Tunnel, built hundreds of feet below the ocean floor, carries up to 1 billion gallons of wastewater from the plant out into the deep Atlantic waters of Massachusetts Bay. And gravity, rather pumps or machines, is the force powering that flow. The tunnel was billed as the longest single-entrance (or dead-end) tunnel in the world, and it is the largely unknown workhorse behind the multi-billion dollar court-ordered cleanup of the harbor that has transformed Boston. But at the end of a decade of construction, handled by some of the country's top designers and contractors, the massive tunnel would not work until someone figured out how to tackle one final and extremely hazardous task.

 

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The tunnel shrunk down in diameter from 24 feet to 5 feet.

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The tunnel was at this point mostly dry, except for knee-deep standing water.

 

 

The Diver Mission

When the best and brightest minds behind the project couldn't agree on how to solve the last piece of the puzzle, they looked outside for help. The job was to remove 55 large safety plugs that had been installed at the end of the tunnel. So a team of commercial divers was dispatched on this mission to yank the plugs. The job would have been difficult yet doable except for one important working condition. All the utilities in the tunnel -- the ventilation, lighting, and transportation, which work crews had relied on for the years when they were building the tunnel -- had by now already been removed. So the divers would have to travel nearly 10 miles into a pitch-black, oxygen-starved tunnel. The tunnel was 24 feet wide at the start, but it grew more an more narrow, until it was just five feet in diameter at the end. And then the divers would have to crawl into a series of thirty-inch-wide pipes to remove the plugs. Because that distance was too far to rely the conventional supply of bottled air, the diving company's project manager came up with an experimental system whereby the divers would need to mix their breathing air in the tunnel, using the vapors from tanks of liquid oxygen and liquid nitrogen. They relied on souped-up Hummer Humvees to get them part way into the tunnel. But when it became too narrow, they had to trudge along on foot, lugging their equipment with them, in the dark.

 

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Divers took special Humvees for part of the journey.

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They were given an experimental mixed-gas breathing system.

 

 

The Dive Team

The team for this hazardous mission was cobbled together from two small diving companies, one from the West Coast and the other from the East Coast. As a result, the divers were strangers to each other until just before the job began.

 

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DJ Gillis, 29,
Massachusetts

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Tim Nordeen, 39,
Washington

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Billy Juse, 34,
New Hampshire

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Donald "Hoss" Hosford, 24,
Idaho

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Dave Riggs, 38,
Nevada

 

 

*Photos courtesy of MWRA