Central Artery/Tunnel Project

Central Artery/Tunnel Project. Commonly known as "the Big Dig," it was a megaproject in Boston that rerouted the city's central highway, Interstate 93, into a state-of-the-art tunnel system. The project also constructed a new harbor tunnel, the Ted Williams Tunnel, extending Interstate 90 to Logan International Airport. Its primary goals were to alleviate severe traffic congestion, replace an aging elevated highway, and reconnect downtown Boston to its waterfront.

Background and planning

The project's origins trace to the 1950s with the construction of the elevated John F. Fitzgerald Expressway, which quickly became notorious for congestion, dividing neighborhoods like the North End from the city center. By the 1970s, studies by the Massachusetts Department of Public Works and the Federal Highway Administration identified the need for a comprehensive solution. Key political figures, including Governor Michael Dukakis and later Governor William Weld, championed the project through complex federal and state legislative processes. The final environmental impact statement was approved in 1985, setting the stage for one of the most ambitious urban infrastructure endeavors in American history.

Construction and engineering

Construction began in 1991 under the management of a joint venture between Bechtel and Parsons Brinckerhoff. The engineering challenges were immense, requiring continuous traffic flow in one of the nation's oldest cities while building beneath active rail lines, historic buildings, and the MBTA subway system. Innovative techniques like slurry wall construction and the use of a massive tunnel-boring machine were employed. A critical and complex operation involved sliding the pre-cast roof of the I-93 tunnel into place over existing railroad tracks near South Station. The project also involved extensive utility relocation and coordination with agencies like the United States Army Corps of Engineers for work near the harbor.

Costs and financing

Initially estimated at $2.8 billion in 1985, the final cost ballooned to over $14.8 billion, making it the most expensive highway project in the United States. Financing was a complex mix of federal and state funds, with significant contributions from the Federal Highway Administration through the Interstate Highway System program. The Commonwealth of Massachusetts issued bonds and implemented toll increases on facilities like the Tobin Memorial Bridge and the Sumner Tunnel to cover overruns. The dramatic cost escalation became a major political issue, leading to congressional hearings and intense scrutiny from the United States Department of Transportation and the Massachusetts Turnpike Authority.

Impact and legacy

The project successfully removed the unsightly elevated highway, opening up over 300 acres for redevelopment and creating new public parks like the Rose Fitzgerald Kennedy Greenway. It significantly improved traffic flow in the core downtown area and reduced vehicle emissions in surrounding neighborhoods. However, its legacy is mixed due to its extreme cost, lengthy duration, and a fatal ceiling panel collapse in 2006 in the I-90 connector tunnel, which led to a massive vehicle recall by General Motors and criminal charges against a concrete supplier. The project remains a seminal case study in civil engineering, public administration, and urban renewal, influencing subsequent megaprojects worldwide.

Major structures

The project's key engineered structures include the Thomas P. "Tip" O'Neill Jr. Tunnel, which carries the submerged I-93 through downtown Boston. The Ted Williams Tunnel extends I-90 under Boston Harbor to East Boston and Logan International Airport. The Leonard P. Zakim Bunker Hill Memorial Bridge, a distinctive cable-stayed bridge designed in part by Santiago Calatrava, serves as the northern gateway. Other significant components are the I-90 interchange in Allston, the I-93/I-90 interchange in South Bay, and the renovated Dewey Square Tunnel.

Category:Buildings and structures in Boston Category:Tunnels in Massachusetts Category:Transportation in Massachusetts