BOSTON (AP) Sooner or later the question will dawn on most drivers zipping through the Big Dig’s spaghetti-like maze of gleaming underground highways.
Where did all the dirt go?
The answer is scattered across New England, from a sprawling tire dump in Connecticut, to the bottom of a 250-ft. abandoned quarry in Quincy, to a Boston Harbor island that was once the site of a quarantine hospital and a plant to render horses into hides, oils and glues.
But that’s the short answer.
How 17 million cu. yds. of dirt — enough to fill 10 Empire State Buildings — found its way from under the streets and waterways of Boston to sites across the region is a story almost as complex as the building of the miles of underground highway that make up the Central Artery/Third Harbor Tunnel project.
It’s a story that began well before the first shovelful of dirt in 1991, when Big Dig engineers stood in downtown Boston and starting drilling holes.
What lay beneath the surface was an open question. The history of Boston is one of claiming land from sea and marsh. Much of the Big Dig is built through landfill dating back centuries, when city fathers were far less discriminate about what they dumped in the harbor.
Project planners would drill between 2,000 and 3,000 borings, analyzing more than 8,000 individual soil samples to assess stability and look for pollutants and anything else that might be lurking underground.
The next question was how to get the dirt out of the tunnels without bringing the city to a halt — a task made trickier given that many of the underground tunnels were built directly beneath the existing overhead Central Artery.
At first, engineers used a conveyor to remove the dirt. That was soon abandoned for trucks. Big Dig workers built a new haul road to give trucks an exclusive route from downtown to the South Boston waterfront where the soil was unloaded onto barges.
“The number of trucks was going to be overwhelming,” said Christopher Barnett, the project’s self-described “dirt guy.”
Another million cubic yards of dirt was removed from the East Boston end of the new Ted William tunnel and loaded onto barges on that side of the harbor.
In the end, it would take a million truckloads to haul away all the dirt.
The going wasn’t always easy, although designers figured out ways to keep the project moving along.
Whenever workers hit what they believed might be contaminated soil, they would block off the area and take special environmental precautions to remove the soil while construction continued around them.
Getting the soil out of the city was only half the battle.
What to do with enough dirt to fill 17 old Foxboro football stadiums to the brim was an equally tough challenge.
Some wistfully thought of using the city’s tried and true solution of simply dumping it in the harbor, an idea that was quickly nixed.
Luckily, a better idea emerged. Why not use the Big Dig dirt to solve an unrelated problem: open landfills.
By the late 1980s, the state had identified about 100 high-priority landfills that needed to be capped to prevent contaminants from leaking into neighboring soil. Over the next decade, Big Dig dirt would cap more than two dozen landfills in Massachusetts.
One of the biggest sat in the middle of Boston Harbor within sight of Logan International Airport and sitting in its flight path.
Since the early 1700s, city leaders had used Spectacle Island — named for its resemblance to a pair of eyeglasses — as a convenient dumping ground. At various times it has housed a quarantine hospital, a horse rendering facility, a trash incinerator and a center to reclaim grease from garbage.
City leaders looking to cap the island turned to the Big Dig. During the course of the project, approximately 3.7 million cu. yds. of soil was dumped there, raising the island’s height by approximately 55 ft.
The island, with 5 mi. of walking trails and a new pier, is now one of the city’s newest parks, reachable by boat.
In nearby Quincy, dirt from the Big Dig was used to solve another dangerous eyesore — a 250-ft. deep abandoned quarry. In 1997, investigators drained the quarry in search of the body of a women believed murdered. They didn’t find the woman’s body, but did uncover a river of debris.
Workers started dumping Big Dig soil into the hole in 2000. Approximately 5.4 million cu. yds. later, a new park had replaced the old quarry.
Massachusetts isn’t the only state to benefit. In Connecticut, Big Dig dirt capped five landfills including an infamous 11-acre pit containing millions of old tires, dubbed “Mount Trashmore.” Rhode Island used more than 350,000 cu. yds. to cover a 121-acre landfill in Johnston.
“It’s one of those other stories from the Central Artery project that gets lost in all the talk of cost overruns,” said Matthew Amorello, chairman of the Massachusetts Turnpike Authority, which oversees the Big Dig.
The $14.6-billion Central Artery/Third Harbor Tunnel project includes the Ted Williams Tunnel under Boston Harbor, an underground connection from Interstate 90 to the Williams tunnel, miles of underground highway in downtown Boston replacing the old elevated Interstate 93 Central Artery and the new Leonard P. Zakim Bunker Hill Bridge.
The 17 million cu. yds. of dirt includes 1.5 million yds. of material dredged from the bottom of Boston Harbor, which was dumped in the ocean and another 1 million still to be removed.