Massachusetts Turnpike Authority
Facts & Figures
Facts & Figures
A few facts and figures about America's most ambitious public works project:
Traffic
Dirt
Concrete and steel
First, most, biggest
Parks and open space
Underground Utility Relocation
Odds and ends
Traffic
The elevated Central Artery had just six lanes. The new underground expressway
has eight to ten lanes.
Altogether, the CA/T project built 161 lanes miles of highway in a 7.5 mile corridor,
about half in tunnels, including four major highway interchanges.
The old road had 27 on- and off-ramps; the new one has just 14. With an improved
surface street system, local traffic exits the main highway and distributes itself
on surface roads while through traffic moves more easily under the city.
The elevated highway carried about 75,000 vehicles a day comfortably when it
opened in 1959. By 2000, it carried more than 190,000, quite uncomfortably. Traffic jams lasted
eight to ten hours a day, with an accident rate four times the national average
for urban interstates. If nothing were done, traffic would have jammed in stop-and-go
misery for 15 to 16 hours a day -- every waking hour -- by 2010.
The underground Central Artery will carry about 245,000 vehicles a day by 2010,
with the Ted Williams Tunnel carrying about 98,000 vehicles a day. There will be normal urban rush hours
of a couple of hours in the morning and evening on the underground expressway,
with traffic moving at about 30 mph.
Back to the Top
Dirt
The project is excavating a total of 16 million cubic yards of dirt, enough to fill Foxboro Stadium (where
the New England Patriots football team and Revolution soccer team play) to the
rim 15 times.
About two-thirds of the dirt was trucked to landfills and other sites. Moving
all that dirt took more than 541,000 truckloads. If all those trucks were lined
up end to end, they'd back up 4,612 miles. That's all the way to Brasilia, capital
of Brazil, as the crow flies, or to the Panama Canal strictly over land.
The rest of the dirt, more than 4,400 bargeloads of it, went to Spectacle Island in Boston Harbor, where an old dump was capped to make way for a new park.
Nearly 3 million cubic yards of clay was made available to cities and towns to
cap landfills that had reached capacity.
For more about what was dug, see "What are we Digging."
Back to the Top
Concrete and steel
The project placed 3.8 million cubic yards of concrete, enough to build a sidewalk
three feet wide and four inches thick from Boston to San Francisco and back three
times.
The project installed more than 26,000 linear feet of steel-reinforced concrete
slurry walls, which formed the walls of the underground highway as well as the supports for
the elevated highway during construction. That's five miles of slurry walls, the
largest application of this construction technique in North America, all resting
on bedrock up to 120 feet below the streets of the city.
Reinforcing steel used in the project would make a one-inch steel bar long enough
to wrap around the earth at the equator.
Elevated Central Artery demolition will remove enough structural steel to make
five Tobin Bridges.
Back to the Top
First, most, biggest
The South Boston connection (or interface) between the underwater section of
the Ted Williams Tunnel and the land-based approach was built in the widest and
deepest circular cofferdam in North America. A ventilation building was built
inside the cofferdam, a watertight structure from which water was pumped so that
construction could take place inside.
The Ted Williams Tunnel interface in East Boston between the land-based approach
and the underwater portion is 90 feet below the surface of Boston Harbor, the
deepest such connection in North America.
The project's seven-building ventilation system is one of the largest highway
tunnel ventilation systems in the world.
Traffic using the Metropolitan Highway System (including the underground Central
Artery, the Ted Williams Tunnel, and the Mass Turnpike out to Route 128) 8is
monitored by the most advanced traffic management and incident response system in the world. Radio and cellular phone signals
are re-broadcast into the tunnels.
The Leonard P. Zakim Bunker Hill Bridge is the widest cable-stayed bridge in the world and the first hybrid and asymmetrical
design in the United States, using both steel (in the main span) and concrete
(in the back spans).
The project required the largest use of segmental bridge construction and the
largest application of steel box girders in the United States.
Crossing the Fort Point Channel included the most extensive use of concrete immersed tube tunnels in the United States, the first installation of jacked vehicle tunnels in North America (and one of the largest in the world), and the second use of
soil mix construction on the East Coast (the first use came in East Boston on
the Ted Williams Tunnel).
The project included the largest geotechnical investigation, testing and monitoring
program in North America. The purpose was to identify conditions in the path of
tunneling work, and help prevent buildings from settling during the digging.
Back to the Top
Parks and open space
The project will create more than 300 acres of new parks and open space, including 27 acres where the existing elevated highway stood,
105 acres at Spectacle Island, 40 acres along the Charles River, and 7 acres as part of an expanded Memorial Stadium Park in East Boston.
Three quarters of the 27 downtown acres will remain open. The rest will be set
aside for modest development, including retail, commercial, and housing uses in
low-rise buildings.
More than 2,400 trees and 26,000 shrubs were planted at Spectacle Island. Another
2,400 trees and more than 7,000 shrubs will be planted downtown.
Back to the Top
Underground Utility Relocation
The project's underground utility relocation program moved 29 miles of gas, electric,
telephone, sewer, water, and other utility lines maintained by 31 separate companies.
All told, about 5,000 miles of fiber optic cable and 200,000 miles of copper telephone
cable was installed.
The Central Artery/Tunnel Project used the latest applications for preventing
damage to Boston's vital subsurface infrastructure. Damage prevention efforts were
continually being updated.
 |
This is one of the most densely populated utility locations in the city at the
intersection of Congress Street and Atlantic Avenue. Shot in 1998, this shot shows
nine live utilities and one abandoned utility in one typical trench excavation.
|
These renderings below show the jumbled mix of utilities before construction, and the lines now set in modern utility corridors.
Click either of these two image for larger versions.
Also, see a photo and details about a special compressed-air excavator (in our equipment section) aimed to cut utility damage.
Related link: Underground Focus Magazine.
Back to the Top
Odds and ends
Because of the new highway system, Boston's carbon monoxide levels will drop 12 percent citywide. How can a road carrying more cars reduce pollution? Because it will keep traffic moving, so that emissions will be reduced significantly.
The cable-stayed bridge across the Charles River used 1,820 miles of steel wire to form the seven-wire strands that are in turn bound together to form the support cables, the largest a foot in diameter.
About 150 cranes were in use project-wide.
The first 25 percent of construction took five years to complete, the second 25 percent took about two years to complete (the half-way point was reached in the spring of 1999). By the summer of 2004, construction was 94 percent complete.
During the peak of construction (1999 through 2002), about $3 million of work was completed each day.
At the peak of construction activity about 5,000 construction workers were on the job.
The deepest point of the underground highway is 120 feet down, beneath the Red Line subway tunnel at Dewey Square (Atlantic Avenue and Summer Street). The highest point is at State Street, where the highway passes over the Blue Line subway tunnel and the roof of the highway is the street above.
The project included 118 separate construction contracts, with 26 geotechnical drilling contracts.
Back to the Top