How Much Did Boston’s Big Dig Cost to Build

Ballpark Estimate: $15 billion

With a population of some 2.8 million people, Boston Massachusetts has long been the center of New England’s educational institutions, the Performing Arts, and professional sports. However, along with that distinction Boston was also known for its world-class traffic congestion. The Central Artery Tunnel Project, more commonly known as the “Big Dig”, was Boston’s’ solution to the growing traffic problem.

An Antiquated Interstate

This was particularly the case for the estimated 200,000 vehicles a year that clogged a short 1.5 mile, six-lane section of I-93 located in the heart of downtown Boston. Interstate-93 was a 40-year old steel and concrete elevated highway and the principal conduit that funneled traffic from the northern part of the state, across the Charles River, and into the city. Called the Central Artery, the day-long congestion was exacerbated not only by the sheer volume of vehicles but also by the design of the highway which included numerous entrances and exits, merging lanes that continuously commingled traffic, and tight turns. As a result, the accident rate was reported to be four times the national average for urban interstates. The same problem existed for motorist trying to get to Logan International Airport through the Callahan and Sumner tunnels under Boston Harbor. In fact, conditions were so bad that if present conditions continued, traffic jams of 16 hours were predicted for 2010.

The “Big Dig”

To avoid the prospects of this enormous gridlock and the dire repercussions that were sure to follow, environmental impact studies were conducted on an enormous highway construction project first conceived in the 1970s. Once federal funding for this incredible engineering feat was secured, in 1991 ground was officially broken for the massive project known today as “The Big Dig”.

Tunnel Objectives

Northbound Tunnel

The first task was to replace the 1.5 mile section of the elevated highway coming into downtown Boston from the north with a new eight to ten-lane expressway that now moves the vehicle traffic under the city through a 3.5 mile tunnel. This phase of the project was completed in 2003 and incredibly, while the new tunnel was being built directly beneath the existing elevated section, the construction was accomplished without seriously restricting the traffic flow still flowing into Boston. In addition, five major interchanges were constructed to direct traffic at Logan Airport and in various other locations in the North and Southern areas of Boston.

James River Bridge

To accommodate the southbound traffic coming from the north along I-93 and US-1, a new ten-lane bridge was built across the James River that leads directly into the northern end of the tunnel. Called the Leonard P. Zakim Bunker Hill Bridge, it is the widest “cable-stay” bridge in the world. (A cable-stay bridge is one which suspends the roadbed from cables running directly to the towers instead of from cables slung over the towers.) In fact, this bridge is the first in America to employ a cable-stayed design and because of this unique feature has quickly become a picturesque icon for the city of Boston.

Ted Williams Tunnel

To reduce the commuter traffic through the Callahan and Sumner Tunnels to Logan International Airport, the only direct access to the airport from the city, a connector-highway was added to the Massachusetts Turnpike. In addition, this new connector now carries vehicle traffic into a third tunnel constructed under Boston Harbor from downtown Boston directly to US-1A in East Boston and to the airport. Called the “Ted Williams Tunnel”, it has four-lanes, is 1.6 miles in length and since it’s opening to commuter traffic in 1995, imposes a toll-charge for all westbound traffic.

Rose Fitzgerald Kennedy Greenway

Once the construction of the Central Tunnel under downtown Boston was completed, named the Thomas “Tip” O’Neill Tunnel, the antiquated 1.5 mile section of elevated highway was closed and dismantled in 2004. In its place the Rose Fitzgerald Kennedy Greenway is presently under construction. The 30-acre Greenway is the final phase of the project and will consists of a new tree-lined boulevard and cross streets, sidewalks, several parks and public spaces extending nearly one mile through the heart of Boston. Also planned are open lawns, gardens, grand fountains, shaded terraces, and footpaths in a shrub-filled setting that will host marketplaces for local entrepreneurs, art shows, and other similar events.

The Latest Cost Figures

Although the initial estimate for the project in 1985 was around $3 billion, inflationary increases due to multiple beaurecratic delays and from many cost overruns, the total current 2007 budget is approximately $15 billion. In this regard, it is by far the most expensive public project ever undertaken. Established to report on the cost, schedule and safety of the project, a Project Management Monthly (PMM) meeting is held periodically with senior management and a report is issued on the projects principal milestones. According to the latest report (August 1997), the $14.798 billion is divided as follows in millions:

• Constructions – $9,651
• Project Management – $2,259
• Section Design Contracts – $1,062
• Insurance Expenses – $624
• Right Of Way Settlements – $590
• Force Accounts – $588
• Contingency – $25

Of that total amount $14.627 billion has already been committed with $172 million left for the estimated 265 remaining invoices.