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What Lessons Can Be Learned from the Boston Big Dig?



The lessons learned from the Boston Big Dig highlight the need to have a thorough construction plan that is thoroughly reviewed, questioned, analyzed and vetted before moving forward.


The Boston Big Dig is notorious for its scale, scope, mistakes, and feats of construction engineering. As a result, there are many lessons that can be learned from this project that are directly applicable to every construction project, regardless of size and budget.


This blog post is the first in our new series focused on lessons learned from large-scale projects. By taking a close look at these construction projects, our hope is that the highlighted lessons can be used to improve  the decision making process before we start to dig.


The Facts on the Boston Big Dig


Boston’s Central Artery/Tunnel Project is known internationally as the Big Dig. This project is the largest, most involved, and technically challenging highway construction project in American history.


In fact, the rebuilding of how Boston motorists travelled through the city is a bigger project than the Panama Canal, Hoover Dam, and the Alaska Pipeline projects. And it ran through the very heart of one of America’s busiest and congested cities.


The Big Dig is renowned not only for its cost overruns and massive problems but for its engineering feats including:


  • The deepest underwater connection.

  • The largest slurry-wall application and usage ever in North America.

  • The usage of ground freezing.

  • The extensive deep-soil mixing applications used to stabilize the tenuous Boston soil.

  • The world’s widest cable-stayed bridge.

  • The largest tunnel-ventilation system in the world.

Accomplishing just one of these engineering projects would be a massive accomplishment for any construction and engineering project. But to do all of these in one project, without interrupting the flow of traffic, is truly unprecedented.


When it was finally completed in 2007, the Big Dig did give the city of Boston a completely updated infrastructure with new roads, bridges, and tunnels. The city of Boston was dealing with unprecedented traffic gridlock due to a road system that was not designed to handle a growing and booming city.


The barebone facts on the Boston Big Dig highlight the dollars and cent problems with the project:


  • Planning started in 1982.

  • Construction happened from 1991 to 2006.

  • The Big Dig was completed on December 31, 2007.

  • The project was originally scheduled for completion in 1998.

  • The original estimated cost was $2.8 billion.

  • The final project cost was $14.6 billion.

  • The Boston Globe estimates the Big Dig will ultimately cost $22 billion (with interest) and that it won’t be paid for until 2038.

But on the flip side, this construction and engineering mega-project has some impressive facts and figures that can’t be ignored:


  • The project built 161 lane miles of highway, half of this is in tunnels. And includes 4 major highway interchanges in a 7.5-mile corridor.

  • The old road had 27 on-and-off ramps – the new one has 14. The improved infrastructure means that local traffic can exit the highway to surface roads while the through traffic continues under the city.

  • 16 million cubic yards of dirt was excavated. This is enough to fill a stadium to the top 16 times.

  • It took over 541,000 truckloads to move this dirt.

  • The Big Dig placed 3.8 million cubic yards of concrete.

  • The project installed over 26,000 linear feet of steel-reinforced concrete slurry walls. These slurry walls formed the walls of the underground highway and the supports for the elevated highway during construction.

  • The 5 miles of slurry walls is the largest application of this technique in North America. This is all resting on bedrock up to 120 feet below the city streets.

  • This project required the largest use of segmental bridge construction and the largest application of steel box girders in the United States.

  • The Big Dig created more than 300 acres of new parks and open spaces.

  • The project’s underground utility relocation program moved 29 miles of utility lines. These lines are maintained by 31 separate companies. About 5,000 miles of fiber optic cable and 200,000 miles of copper telephone cable were installed.

All facts and figures from The Big Dig: Facts and Figures, from mass.gov.  


So, what does this tell you?


It tells us that the very scope of this project, set it up for failure.


While the end result was ultimately a success – with traffic congestion in the city center being relieved – there were many problems along the way that unfortunately cloud the project goals.


What Went Wrong with the Boston Big Dig


From the outset, the planning, scoping, engineering and construction plans, and materials plans were flawed. There is not one single item that resulted in the mistakes, cost overruns, delays, and firings during the Big Dig project.


As highlighted in The Big Dig: Learning from a Mega Project, there were a number of factors that contributed to the construction, engineering, and management errors:


  • An unrealistic cost estimation – neglecting to fully consider the impacts of inflation on the project.

  • A failure to fully understand and assess the subsurface conditions during the construction process. The challenges presented by the subsurface were grossly underestimated.

  • The size of the project combined with the fact that it was being done in the middle of a very busy and congested city resulted in many unanticipated slow-downs, costs, changes, and mistakes.

The Big Dig was knee-deep in surprises and unexpected construction and engineering conditions, that resulted in further problems, delaying and adding more cost.


  • Uncharted utilities.

  • Archeological discoveries.

  • Unexpected ground-water conditions.

  • Environmental problems.

  • Weak soil.

  • Unexpected hazardous materials.

These all resulted in health and safety problems, materials issues, budgetary overruns, design changes, and schedule delays – not to mention the drain on human resources.


The discovery of the 150-year-old revolutionary-era sites and North American artifacts resulted in further construction and engineering complications, delays in permits and approvals, and the involvement of a range of stakeholders including historical and preservation organizations and Native American groups.


There wasn’t just one thing that went wrong with the Big Dig.


The sheer scope of the project, the involvement of numerous construction and engineering firms, the involvement of various levels of government, and the pressure to have the project completed sooner than later meant that the Big Dig faced impossible barriers from the very outset.


What Lessons Can Be Learned from the Boston Big Dig?


The lesson learned from the Boston Big Dig emphasize the importance of the key principles of sound construction and engineering management practices:


  • Independent cost engineering/estimation is critical.

  • Inflation can never every be overlooked.

  • Scope creep can ruin even the most well-planned project.

  • Project standards must be maintained at all times.

  • Communication is critical.

The PCS Approach to Construction Projects


While we cannot claim to have all the answers for what wrong with the Big Dig project, we can take many lessons from this project that we apply to your construction projects and requirements.


Know that PCS is your trusted construction cost advisor through-out all phases of construction.

Trust PCS to:


  • Assist with feasibility studies and review designer sketches and measurements to determine project scope.

  • Study architect and engineer plans, determine the costs involved, and set an overall estimated budget.

  • Benchmarks your project with others like it.

  • Plan costs to help the design team stay within the project or program budget using an iterative process.

  • Prepare a final Opinion of Probable Cost report.

  • Assess cost effects when project changes occur.

  • Resolve scope creep with contractors.

  • Manage and resolve disputes between suppliers, contractors, and designers.

  • Provide a thorough review of the project showing the actual costs.

At PCS, Construction Is Personal™. We want you to know that we care about your construction project. We will listen to you and work for you to ensure that your construction project is successful.



About the author 


Lee Thomas, MBA is the chairman and CEO of Project Cost Solutions. Lee has over 20 years of hands-on operational process experience under his belt. He is deeply committed to seeing your construction project succeed.

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