History of the Big Dig

Big Dig is the unofficial name of the Central Artery/Tunnel Project (CA/T), a megaproject which rerouted the Central Artery (Interstate 93), the chief controlled-access highway through the heart of Boston, Massachusetts, into a 3.5 mile (5.6km) tunnel under the city. This project was developed in response to traffic congestion on Boston's historically tangled streets, which were laid out long before the advent of the automobile. By mid-20th century, car traffic in the inner city was extremely congested, with north-south trips especially so. Commissioner of Public Works William Callahan pushed through plans for an elevated expressway which eventually was constructed between the downtown area and the waterfront. This "Central Artery" (known officially as the John F. Fitzgerald Expressway) displaced thousands of residents and businesses and physically divided the historical connection between the downtown and market areas and the waterfront. Governor John Volpe interceded in the 1950s to send the last section of the Central Artery underground, through the Dewey Square (or "South Station") Tunnel, but while traffic moved somewhat better the other problems remained.

Built before strict federal Interstate Highway standards were developed during the Dwight D. Eisenhower administration, the expressway was plagued by tight turns, an excessive number of entrances and exits, entrance ramps without merge lanes, and continually escalating vehicular loads. Local businesses again wanted relief, historians sought a reuniting of the waterfront with the city, and nearby residents desired removal of this "Green Monster". ("Its matte green paint prompted Thomas Menino to call it Boston’s 'other Green Monster'." The original Green Monster is Fenway Park's left field wall”.) [cite news | author=Associated Press | url=http://msnbc.msn.com/id/3769829 | title=Boston’s ‘Big Dig’ opens to public | publisher=MSNBC | date=2003-12-20 | accessdate=2006-07-18] M.I.T. engineers Bill Reynolds and (eventual state Secretary of Transportation) Frederick P. Salvucci envisioned moving the whole expressway underground.

Cancellation of the inner belt

Another important motivation for the Big Dig in its final form was the abandonment of the Massachusetts Highway Department's intended expressway system through and around Boston. The Central Artery, as part of MassHighway's Master Plan of 1948, was originally planned to be (and signed as) the downtown Boston stretch of Interstate 95, with a bypass road called the Inner Belt (officially Interstate 695) to pass around the downtown core to the west, through the neighborhood of Roxbury and the cities of Brookline, Cambridge and Somerville. However, earlier controversies over impact of the Massachusetts Turnpike Boston extension, particularly on the heavily populated neighborhood of Brighton, and the large number of additional homes that would have had to be destroyed led to massive community opposition to both the InnerBelt and the Boston section of I-95.

Clearances for I-95 through the neighborhoods of Roxbury, Jamaica Plain, and Roslindale led to secession threats by Hyde Park, Boston's southernmost neighborhood (and the one most recently added to the city, in 1912). By 1972, however, with only a minimum of work done on the I-95 right of way and none on the potentially massively disruptive Inner Belt, Governor Francis Sargent put a moratorium on highway construction within the MA-128 corridor, except for a short stretch of Interstate 93. In 1974 the remainder of the Master Plan was canceled, leaving Boston with a severely overstressed expressway system. With ever-increasing traffic volumes funneled onto I-93 alone, the Central Artery became chronically gridlocked. The Sargent moratorium led to the rerouting of I-95 away from Boston around the MA-128 beltway and theconversion of the cleared land in the southern part of the city into the Southwest Corridor linear park and a new right of way for the Orange Line subway and Amtrak. Parts of the planned I-695 right of way remain unused and under consideration for future mass transit projects.

The original 1948 Master Plan included a Third Harbor Tunnel plan that was hugely controversial in its own right because it would have disrupted the Maverick Square area of East Boston. It was never built.

Commingling of traffic

A major reason for the all-day congestion was that the Central Artery carried not only north-south traffic, but much east-west traffic as well. Boston's Logan Airport lies across Boston Harbor in East Boston, and before the Big Dig, the only access from downtown was through the paired Callahan and Sumner tunnels. Traffic on the major highways from west of Boston, the Massachusetts Turnpike and Storrow Drive, mostly traveled on portions of the Central Artery to reach these tunnels. Getting between the Central Artery and the tunnels involved short stretches on city streets, increasing local congestion.

The final Big Dig plan, then, combined several projects—the depression and improvement of the Central Artery, the construction of a third Harbor tunnel (now known as the Ted Williams Tunnel), and massive interchange improvements to the Massachusetts Turnpike and several other major routes in the area. While only one net lane in each direction was added to the north-south I-93, several new east-west lanes were added to untangle the traffic. East-west traffic on the Massachusetts Turnpike now proceeds directly through the Ted Williams Tunnel to Logan Airport and Route 1A beyond, with new exits in South Boston along the way. Traffic between Storrow Drive and the Callahan and Sumner Tunnels uses a short portion of I-93, but additional lanes and direct connections are provided for this traffic.

Mass transit

A number of public transportation projects were included as part of an environmental mitigation for the Big Dig. The most expensive was the building of the Phase II Silver Line tunnel under Fort Point Channel, done in coordination with Big Dig construction. Silver Line buses now use this tunnel and the Ted Williams Tunnel to link South Station and Logan Airport.

Promised projects to restore the Green Line streetcar service to the Arboway Line in Jamaica Plain, extend the Green Line beyond Lechmere Station, and connect the Red and Blue subway lines have not been completed as of 2008. The extension beyond Lechmere is in progress, and the Red and Blue subway line connection is being designed; the status of the Arborway Line is unclear.

Yet another plan, the North-South Rail Link that would have connected North and South Stations, the major passenger train stations in Boston, was part of the original Big Dig but was ultimately dropped by the Dukakis administration as an impediment to acquiring Federal funding for the project.

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