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Green Line Extension and the Big Dig

Listen to the GBH Podcast The Big Dig


Monday, December 12, MBTA Green Line Extension Opens.

Did you know that the Green Line Extension is connected to the Big Dig?

At last: the trains have come to Somerville; first new Green Line Station opens

Project promised for Big Dig  The Green Line Extension was part of the state’s mitigation strategy when it negotiated the “Big Dig,” years ago; the public works project that relocated the elevated highways that traversed Boston underground. The train extension was promised to the city residents as part of the project.

Why The Green Line Became Legally Mandated Following The Big Dig  This segment aired on WBUR, May 9, 2016

The tracks of the corridor for the proposed Green Line Extension which run through Somerville and Medford already serves MBTA Commuter Rail and Amtrak trains. The MBTA fiscal control board is considering a scaled-back proposal to extend the Green Line. Consultants hired by the T outlined a new, simpler version of the project. The Green Line would still go to Medford, but instead of full stations, each of the six new stops would have a weather shelter. Instead of the 10,000-foot bike and pedestrian path, it would be cut down to 7,000 feet, and a more simple design.

"Only two years ago it was nothing more than a mountain of garbage in the middle of Boston Harbor, leaking thousands of gallons of toxic material into the surrounding water."   
– Peter Zuk, former CA/T Project Director
Nancy K. O'Loughlin

Meet Nancy K. O'Loughlin, a descendant of Spectacle Island, Her grandfather Peter Reed was born on Spectacle Island. What a pleasure speaking with her at Amesbury Open Studios!

Photos courtesy of Boston Harbor Now

​What happened on Spectacle Island?

For thousands of years, Native American tribes used the island for fishing and clamming until around 1615, when European diseases killed virtually all of the native population. An archaeological dig conducted before the restoration of the island revealed a wealth of information on Native American culture and lifestyle dating from 535 A.D. to 1590. Some artifacts discovered indicate that Native American tribes may have used the island about 8,000 years ago.


The early settlers first used the island as a source of timber and for pasture land. In the early 1700s, the island was used as a quarantine hospital for smallpox victims. Ships coming into the Boston Harbor stopped on the island, and any passengers showing signs of disease had to disembark. In 1847, it was home to two resort hotels that were shut down after officials discovered gambling and brothels. In 1857, a Boston businessman built a horse-rendering factory that processed as many as 2,000 horses a year into glue stock, hair, oil, and bones.


Why is it called Spectacle Island?

Spectacle Island got its name from early European settlers who arrived in Boston in 1630. They noticed the two large mounds of land were connected by a sandbar and looked like a pair of spectacles.


Spectacle Island becomes the city trash dump

​In 1903 after the horse rendering plant closed, it was a grease extraction facility for making soap and glycerin. Boston began using the island as a landfill in 1921. For close to 50 years, toxins were leaking into Boston Harbor, polluting the water. A bulldozer once sank and disappeared into a pile of trash. The city finally closed the toxic, smelly, leaking island in 1959.

Spectacle Island 1950s

Spectacle Island, 1950s. Courtesy of Boston City Archives

Spectacle Isand 1950s

Revitalization of Spectacle Island

Working together, the City of Boston, the Department of Environmental Management, and the Massachusetts Department of Environmental Protection came up with a plan to solve the environmental disaster. Spectacle Island provided a place to dump the excavated material from the tunnels being dug for the Big Dig (Central Artery/Tunnel Project). The result would be to build a new park. Construction began in 1993, and barges loaded with dirt and gravel were shipped to the island. It was capped with two feet of clay and covered with two to five feet of topsoil above the cap for planting new vegetation. Workers planted 2,400 trees and 26,000 shrubs in the fresh soil.

Spectacle Island transformed

The island's environmentally friendly systems include composting toilets with no water or chemicals, electric vehicles, and water from the kitchen and sinks is filtered and used to water the plants. The visitor center with a museum and cafe is powered by solar panels. Adirondack chairs grace the front porch overlooking the harbor with a magnificent view of the Boston skyline. The island opened to the public in June 2006.

Spectacle Island 1952 unloading trash

Spectacle Island, 1952. Courtesy of Boston City Archives

Spectacle Island Renewed

Photo courtesy of Boston Harbor Now/Boston Harbor Cruises

Central Artery Tunnel logo

Northeastern University Library

The Problem

Boston, Massachusetts, had a world-class traffic problem, an elevated six-lane highway called the Central Artery that ran through the center of downtown. When it opened in 1959, the Central Artery carried about 75,000 vehicles a day. It has carried upwards of 200,000 making it one of the most congested highways in the United States. Traffic crawled for more than 10 hours each day. Without major improvements to the Central Artery and the harbor crossings, Boston expected a stop-and-go traffic jam for up to 16 hours a day - every waking hour - by 2010. Traffic wasn't the only problem the old Central Artery caused in Boston. The elevated highway, which displaced 20,000 residents, also cut off Boston's North End and Waterfront neighborhoods from the downtown, limiting their participation in the city's economic life.

The Solution

The project had two major components. One was replacing the six-lane elevated highway with an eight-to-ten-lane underground expressway directly beneath the existing road culminating at the northern point with a 14-lane, two-bridge crossing over the Charles River. The other was the extension of I-90, the Massachusetts Turnpike, from south of downtown Boston with a tunnel beneath South Boston and the Boston Harbor to Logan Airport. The first link of the connection, the four-lane Ted Williams Tunnel under the harbor, completed the 3,089 miles of Interstate 90 from Boston to Seattle, WA.


The Challenges

The Central Artery/Tunnel Project became known as the Big Dig. It is public works on a scale comparable to some of the great projects of the last century, the Panama Canal, the English Channel Tunnel (the "Chunnel"), and the Trans-Alaska Pipeline. Each of these projects presented unique challenges. The Central Artery/Tunnel Project's unique challenge was to construct the roadway in the middle of Boston without crippling the city. The work of the project and its magnitude and duration had never been attempted in the heart of an urban area. Unlike any other major highway project, it was designed to maintain traffic capacity and access to residents and businesses, keeping the city open for business throughout construction.

Building an expressway underground in a city like Boston proved to be one of the largest, most technically difficult, and environmentally challenging infrastructure projects ever undertaken in the United States. The project's 7.8 miles of highway had close to 50 separate designs divided into 118 separate construction contracts, with 26 geotechnical drilling contracts. At the peak of construction, five thousand construction workers were on the project, and workers did about $3 million of work each day. About 150 cranes were in use project-wide. The deepest point is 120 feet and runs beneath the Red Line subway tunnel at Dewey Square. 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 Leonard P. Zakim Bunker Hill Memorial Bridge, a ten-lane cable-stayed bridge over the Charles River, is the widest ever built and the first to use an asymmetrical design.


Along with improved mobility in a notoriously congested city, the Central Artery/Tunnel Project reconnected neighborhoods severed by the old elevated highway and improved the quality of life in the city. Boston's carbon monoxide levels dropped 12 percent citywide. The Big Dig was an engineering feat like no other. It made significant advances in roadway construction and urban planning. It created more than 300 acres of new parks and open space, including the 27 acres of The Rose Kennedy Greenway, more than 100 acres on Spectacle Island where dirt from the project capped the abandoned dump, and 40 acres along the Charles River.


The nation's most complex and costliest highway project, officially came to an end on Dec. 31, 2007 marking the end of the joint venture that teamed megaproject contractor Bechtel/Parsons Brinckerhoff with the Massachusetts Turnpike Authority to build the dizzying array of underground highways, bridges, ramps and a new tunnel under Boston Harbor — all while the city remained open for business.

Big Dig Construction

Big Dig construction courtesy of Boston City Archives

Big Dig Construction

Big Dig construction courtesy of Boston City Archives

Big Dig tunnel underground construction
Big Dig tunnel underground construction

These YouTube videos from MegaStructures Boston Big Dig British Documentary take you deep inside The Big Dig. It's riveting and filled with "glad you didn't know what was happening moments." Take a look

The Big Dig megaproject is jam-packed with history and unique stories across multiple disciplines. These videos present wide-ranging perspectives, interviews, and exploration of one of the most ambitious roadway projects in history, and there are many more intriguing stories of every aspect of the project.

Uncovering Boston Big Dig | CBS "Sunday Morning"  Charles Osgood goes underground to explore Boston's Big Dig, already well on its way to becoming the most expensive highway project in U.S. history.

Boston's Big Dig | Top Stories | CBC  A buried highway in Massachusetts many years late trailing huge cost overruns is a big hit with users in spite of the hefty price tag and toll.

Tour of the Big Dig in Boston  Dan McNichol, the public relations officer for the city, shows Bob Vila "The Big Dig Project."
Big Dig Project  Kurt Soucy

Seattle Tunnel: Lessons learned from Boston’s Big Dig  Despite delays and cost overruns, transportation and infrastructure experts say Seattle has avoided the problems that plagued Boston’s Big Dig.

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