(The Big Dig)

Part 2


The list of top megaprojects with mega-cost overruns reads like a who’s/who of construction’s biggest deals.

  1. The Suez Canal ran 1,900% over the original budget.
  2. The Sydney Opera House came in 1,600% over budget.
  3. The Boston Artery Tunnel (Our old friend, The Big Dig) ran a whopping 196% over budget.
  4. The Great Belt Rail Tunnel was 110 % over the original bid when finally completed.
  5. The Channel Tunnel wins the mega project cost overrun contest at a modest 80% over budget.

In our discussion of why megaprojects experience such a high failure rate, (not coming in on time and on budget) we have categorized the causes into four main areas:

  1. SIZE

In the last two weeks we have covered size and uncertainty; today we take up complexity.


We look at complexity as layers of difficulty.

  • The first layer, and most obvious, is the complexity of the task itself.
  • The second layer we call social complexity, and it refers to the number and diversity of actors communicating and working with each other.
  • And third, cultural complexity encompasses the history, experience, and sense-making processes of the different groups that join their efforts to complete a megaproject.

Using our old friend Boston’s Big Dig to illustrate, let’s take a look at the layers of complexity built into the central artery tunnel project as it was conceived.

Task Complexity – The Big Dig


Task complexity – defined as the density of activities in a given spatial and temporal frame. What did the project entail?

  • First, 1.5 miles of elevated highway was demolished, freeing up 29 acres for attractive boulevards and parks and was replaced by an eight to 10-lane underground expressway which leads into a 14-lane, two-bridge crossing at the Charles River. The road system was designed and constructed to accommodate 245,000 vehicles each day.
  • The larger of the two Charles River bridges, the Leonard P. Zakim Bunker Hill Bridge, a 10-lane, cable-stayed hybrid bridge, is the widest ever built and the first to use an asymmetrical hybrid design (using steel and concrete). At 1,432ft-long, the bridge emerges from the underground Central Artery near the Fleet Center at Causeway Street, crossing the river to make connections with both I-93 and Route 1. The bridge is designed to carry 10 lanes of traffic with 8 lanes passing through the legs of the twin towers and two cantilevered on the east side.
  • The smaller, 4-lane Leverett Circle Connecter Bridge is an 830ft-long bridge constructed of nine box girder sections, the largest in North America, that had to be barged into place and raised by cranes or (in the main span) jacks. The superstructure consists of single steel box girders, 18ft deep at the piers, nine feet deep at center span, and a concrete bridge deck. The substructure consists of two water piers and two land bents, cast-in-place and supported on drilled shafts.
  • The $1.3bn four-lane Ted Williams Tunnel that continues the transport under Boston Harbor, was built using 12 steel sections sunk in a trench to cover the ¾ mile distance.
  • The CA/T’s Operations Control Center (OCC) has one of the most advanced ‘smart highway’ systems in the world. The system uses a range of ITS devices that can monitor all of the traffic in the tunnels, ramps and highways constructed as part of the Big Dig, as well as the majority of other roads and tunnels in Boston. The equipment and facilities used by the OCC include more than 1,400 loop detectors to measure traffic density and identify and project traffic patterns, 430 CCTV cameras, 130 electronic message signboards, 300 lane control signals and carbon monoxide detectors. The computer system has more than 35,000 data points from which to collect data to compile a detailed picture of traffic events.


A complex Undertaking (task) if there ever was one.

Social complexity – The Big Dig

Social complexity – the number and diversity of actors communicating and working with each other. 

  • The overall design and construction management for the Big Dig was provided by a joint venture of Bechtel, Parsons Brinckerhoff, Quade and Douglas.
  • Major heavy-construction contractors on the project included Jay Cashman, Modern Continental, Gannett Fleming Inc, Obayashi Corporation, Perini Corporation, Peter Kiewit Sons’ Incorporated, J.F. White and the Slattery division of Skanska USA (Modern Continental was awarded the largest value of contracts). Power Fasteners provided an epoxy system to hold up concrete roof panels.

Even if you have never participated in a mega project, imagine trying to sort out the individual wants and needs of major international contractors working together on the same project for ten years coupled with the conflicting needs of ten major heavy-construction contractors. If that is not the definition of social complexity, I don’t know what is. Most statisticians would say that it would be impossible to manage the original planned outcomes to a successful conclusion because there are too many moving parts.

Cultural Complexity – The Big Dig

Cultural Complexity – encompasses the history, experience, and sense-making processes of the different groups that join their efforts to complete a megaproject. 

In 1997, the Massachusetts state legislature created the Metropolitan Highway Systemand transferred responsibility for the Central Artery and Tunnel “CA/T” Project from theMassachusetts Highway Department and theMassachusetts Governor’s Office to the Massachusetts Turnpike Authority (MTA). The MTA, which had little experience in managing an undertaking of the scope and magnitude of the CA/T Project, hired a joint venture to provide preliminary designs, manage design consultants and construction contractors, track the project’s cost and schedule, advise MTA on project decisions, and (in some instances) act as the MTA’s representative. Eventually, MTA combined some of its employees with joint venture employees in an integrated project organization. This was intended to make management more efficient, but many believe it just complicated MTA’s ability to independently oversee project activities because MTA and the joint venture had effectively become partners in the project.

That is the definition of “cultural complexity”. The evolving management structure makes italmost impossible to achieve the original intended outcomes for all stakeholders.

The longer we gaze at “The Big Dig” the clearer it becomes as to why most mega construction projects fail to achieve their original objectives. Next week we will cover Institutional Structure.