On July 21, 1999, five deep-sea welders descended one mile down into Boston Harbor and then traversed almost 10 miles beneath the seafloor in a dry sewage tunnel with no breathable air, no light and no chance for rescue should things go horribly wrong, which they did.
This is the story Neil Swidey tells in "Trapped Under the Sea: One Engineering Marvel, Five Men, and a Disaster Ten Miles Into the Darkness," a harrowing account of one of the largest engineering projects in U.S. history and of the hubris and ignorance that led to tragedy. As Mr. Swidey, a writer for the Boston Globe magazine, makes clear, the decision to send men into the "oxygen-starved, toxic tube" was born not of necessity but of "brinksmanship between the contractor building the tunnel and the government agency that owned it."

Trapped Under the Sea

By Neil Swidey
Crown, 418 pages, $26
The opening of the 10-mile-long Deer Island sewage tunnel. MWRA
Boston Harbor's filth is legendary. It was mock-celebrated in the 1966 song "Dirty Water." The city's water-treatment plants were hopelessly inadequate, and barely treated sewage had been pouring into the harbor for decades. The low point was probably Christmas Day 1980, when 50 million gallons of raw waste was accidentally released into the harbor. "Fatigued locals turned to gallows humor to distract themselves from their disgust," writes Mr. Swidey. "They rebranded the tampon applicators floating out of the sewer pipes into the water as 'beach whistles' and the spent condoms as 'Charles River whitefish.' "
The Deer Island Sewage Treatment Plant was supposed to solve these problems. Begun in 1990, the $3.8 billion facility would process human and industrial waste on a small island in Boston Harbor and then send it through a 9.5-mile tunnel into the deep waters of the Atlantic. Fifty-five vertical pipes called risers spurred off the tunnel's final section to further diffuse waste before releasing it into the sea. Temporary safety plugs, likened to giant salad bowls, had been placed near the bottom of each riser to keep water from seeping in before construction was complete.
These plugs were a source of conflict between the tunnel's owner, the Massachusetts Water Resources Authority (MWRA), and the company they hired to build it, Kiewit, "the Omaha-based construction giant" that, Mr. Swidey notes, "had built more miles of the U.S. highway system than any other contractor." The director of MWRA, Doug MacDonald, had left a job as a partner in a Boston law firm to take over the authority, a behemoth of 1,700 employees and, at the peak of harbor cleanup, an additional 3,000 construction workers. Mr. MacDonald's job included mollifying various parties who disagreed about how the Deer Island project would reach completion: Kiewit; the tunnel's designers, mostly out of the picture by 1998; ICF Kaiser Engineers, hired by MWRA to protect its interests and act as Mr. MacDonald's eyes and ears; the union "sandhogs" who bored out 2.4 million tons of rock to create the tunnel; the Occupational Safety and Health Administration, ostensibly looking out for worker safety but seeming more interested in handing out fines; and, though federal funds for harbor cleanup had long since dried up, "a bow-tied federal judge who served as the cleanup project's robed referee, threatening stiff fines or worse if the deadlines he imposed were not met."
The removal of the safety plugs would require a worker to shimmy on his belly inside each 30-inch-wide riser; remove the bolts, O-rings and gaskets; and then drag the 65-pound plug out backward: difficult work that each party involved in the tunnel construction denied was its responsibility.
The problem weighed most heavily on Kiewit. The firm was contractually obligated to deliver on time, subject to late-fee penalties of $30,000 a day, and to cover cost overruns. More, Kiewit had fronted the construction costs and would only be paid by selling the tunnel, piece by piece, to MWRA. The contract further obligated Kiewit to provide "lighting and ventilation (or breathing apparatus) for the personnel" that pulled the plugs but, in what seemed a senseless conflict, mandated that the plugs "could be removed only after the tunnel was completed," writes Mr. Swidey, "meaning after the sandhogs had cleared out, taking their extensive ventilation, transportation, and electrical systems with them."
Kiewit protested that clearing the tunnel of its life-sustaining infrastructure would make "the risk of catastrophe [to the workers pulling the plugs] . . . exponentially higher !" They offered several sound alternatives. In response, ICF Kaiser accused them of just wanting their payday. After a "year-long memo war," Kiewit capitulated, cleared the tunnel and hired a commercial dive team to go into a pitch-black airless tube.
"[They] were simply continuing a tradition where blue-collar workers are the ones expected to transform the dazzling dreams of engineers and the promises of politicians into concrete reality," Mr. Swidey writes.
The hard hats—DJ, Tim, Hoss, Riggs and Billy—were full-time commercial divers, men who among them had decades of experience in tunnels, on bridges, offshore oil-rigs and salvage missions. If several partied a little too much, they were nevertheless tough and reliable all, the kind of men you'd want at your back when trouble started. Except that rule No. 1 is that you can't save your fellow man in a confined space with the air running out. Training to descend into the tunnel, the men were told that even one or two breaths of the toxic air would be fatal. "The message to the divers was clear," writes Mr. Swidey. "You must not add to the body count."
The training took place in the backyard of a small New Hampshire commercial dive operation owned by Tap Taylor. Kiewit decided to have him work under a Washington state company called Norwesco. Crucial to Norwesco winning oversight on the job was its pitch to use "a cutting-edge system" conceived by Canadian engineer Harald Grob. Based on a Danish device called the MAP Mix 9000, the system would blend liquid oxygen and liquid nitrogen into a breathable gas. Though it had never been put into service, Mr. Grob made assurances that his approach would provide as much breathable gas as a far heavier conventional supply. "So the liquid option," writes Mr. Swidey, "would spare the divers a whole lot of lugging."
And yet, as the men readied the Humvees they would lower into the tunnel, and as they snaked thousands of feet of 3/8 -inch hose that would tether them to the MAP Mix, they still had not seen the new breathing system. Mr. Grob ignored their questions and concerns and placated his Norwesco boss by saying that a key component had yet to arrive from Europe, that everything would be fine.
It was not. When the MAP Mix arrived it looked like nothing so much as "an old-model toaster oven." There was no time to test it. Increasingly apprehensive, the divers confronted the inventor: Was he sure the Map Mix would work? Thin-skinned, with a marked "lack of social skills," Mr. Grob brushed them off. He was sure, and into the hole the men went.
Barely anything but the men and their resolve functioned as it should have. An engine stalled, air hoses tangled and a first arduous slog down the tunnel was aborted before any plugs were pulled. On the second day, the men managed to yank out two. The third day was when the horror show started. Tim and Billy handled the Humvees—one always towing the second facing backward, as it was too confined to turn around—that transported the men as deep as the narrowing tunnel allowed. Hoss, DJ and Riggs walked the rest of the way. They managed to remove the third of the 55 plugs before their oxygen started getting thin. DJ and Riggs slumped to the ground. On the verge of passing out, Hoss radioed back to the Humvees: What was going on with the air supply? The reply was an expletive, and the line went dead. With his almost dying breath, Hoss switched the three men's breathing source from the MAP Mix to the back-up oxygen, after which they recovered and trudged full of dread back to the Humvees. Tim and Billy were dead. They'd died instantly after getting "a pure shot of nitrogen" when the MAP Mix froze.
Why did the breathing system fail? Because the MAP Mix 9000 wasn't designed for use on people but for packaging cheese and burritos, "to give them a sort of vacuum seal that would lead to longer shelf life," writes Mr. Swidey. Mr. Grob had dismantled the device and changed its settings despite bold type on page one of the user's manual warning against just this. More, he had instructed Tap Taylor to adjust the settings on the handheld gas monitors in order that their alarms and flashing lights "wouldn't be going off constantly, making it hard to get work done." They would not be triggered until the oxygen level dropped to 6%—the death zone. The divers had been human canaries.
Norwesco moved quickly to shift the blame. Mr. Grob's credulous boss said he'd come to believe that "[Grob] didn't know what was doing." If no one at Norwesco appreciated that their lack of accountability was problematic, possibly criminal, others did. Mary McCauley, the state trooper who led the death investigation, felt Mr. Grob "had shown willful disregard for the lives of the divers." Joan Parker, safety director in the Massachusetts attorney general's office, wanted to bring manslaughter charges against him but found, after months of investigation, that the AG's office wouldn't prosecute. "She also couldn't help but wonder," writes Mr. Swidey of Ms. Parker, "if Boston's power brokers, who were desperate to end the tortured saga of the harbor cleanup, were applying pressure to avoid a potentially messy criminal prosecution." The three surviving divers, crushed by guilt, were awarded damages when what they wanted was justice. But there can be no justice; only a cautionary tale, which Mr. Swidey writes with splendid heart.
And there remained the need to pull the remaining plugs. The solution, which I will not spoil, came not from an engineer but from MWRA's Doug MacDonald, as desperate as anyone to solve the problem and avoid additional casualties on his watch. His self-described "crazy idea" worked better and faster than anyone expected, and it is bracing to see it succeed in the wake of so much hardship.
—Ms. Rommelmann is the author of "The Queens of Montague Street," a memoir of growing up in 1970s Brooklyn Heights.