Work began on the project’s Final Environmental Impact Statement/Report (FEIS/R), a required review for major federally funded highway projects. This step framed the core idea: replace the aging, congested elevated Central Artery (I-93) with a largely underground route and related harbor and interchange upgrades.
The FEIS/R was filed, documenting the expected transportation, neighborhood, and environmental effects of the proposed highway and tunnel work. Filing the FEIS/R helped move the project from concept toward federal approval and detailed design.
Bechtel/Parsons Brinckerhoff began work as the project’s management consultant. This established the management structure for a multi-decade effort that would coordinate design, construction staging, and contracts while keeping traffic moving through downtown Boston.
Congress approved federal funding and the project’s basic scope, a major turning point because the work depended on large federal highway dollars. With funding authority in place, planning and design could proceed toward construction commitments.
With the project moving toward construction, final design work proceeded and exploratory archaeology digs began. These steps reflected how building under a historic city required both engineering design and careful handling of cultural resources.
The Federal Highway Administration issued a Record of Decision (ROD), which is the formal federal approval allowing the project to move into construction. This decision marked the shift from planning and review to building major new highway and tunnel infrastructure.
Construction started on the South Boston Haul Road (a bypass route for construction trucks) and the third harbor crossing that would become the Ted Williams Tunnel. Early work focused on creating space and logistics to build large underground structures while limiting disruption in nearby neighborhoods.
The Ted Williams Tunnel opened on schedule for commercial traffic, providing a new Boston Harbor crossing and expanding cross-harbor capacity. This was the project’s first major operational milestone and demonstrated that large tunnel segments could be delivered and used while the rest of the system was still under construction.
The I-90 extension and connector opened, linking the Massachusetts Turnpike into the Ted Williams Tunnel and improving access to Logan International Airport. This opening shifted major travel patterns by moving more airport-bound traffic away from surface streets and older connections.
The northbound lanes of the new downtown I-93 tunnel (later named the Thomas P. O’Neill Jr. Tunnel) opened. This was a key step in replacing the elevated Central Artery with an underground route, allowing traffic to begin shifting off the older structure.
The Leonard P. Zakim Bunker Hill Memorial Bridge opened northbound lanes, creating a new signature river crossing tied into the rebuilt I-93 corridor. The bridge helped complete the reconfigured approach to downtown by providing wider capacity and modern connections to the tunnel system.
The southbound lanes of the I-93 tunnel opened, completing a major part of the downtown traffic shift into the underground expressway. With both directions operating, Boston could move closer to removing sections of the elevated highway above.
After major tunnel openings, demolition of the old elevated highway advanced, clearing space for surface rebuilding and future parkland. Removing the elevated structure was important not just for traffic flow, but for reconnecting downtown with nearby neighborhoods that had been divided for decades.
The last major downtown ramp connection opened, marking “majority completion” of the highway system from a driver’s perspective. This milestone signaled that the rebuilt network of tunnels, ramps, and interchanges was largely functioning as intended, even as remaining surface and closeout work continued.
A suspended concrete ceiling section in the I-90 connector tunnel failed and fell onto a car, killing a passenger and injuring the driver. Investigators determined the probable cause involved epoxy anchor adhesive that could not sustain long-term loads (poor creep resistance), prompting closures, repairs, and intensified safety scrutiny.
The Central Artery/Tunnel Project formally concluded after remaining construction, contract closeout, and system completion tasks were finished. By this endpoint, Boston’s main highway route through downtown had shifted from an elevated structure to a tunnel-and-bridge system, setting the stage for new surface streets and long-term redevelopment of the former elevated corridor.
Boston's Central Artery/Tunnel Project (Big Dig) timeline (1982–2007)