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Hard lessons from the Big Dig
April/May 2003
It has been described at the most expensive public works project ever undertaken in the US - but Boston's Central Artery/Tunnel project, commonly known as the "Big Dig" is now running seven years late and $US12 billion ($AU 20.3 billion) over its original budget estimate of $US 2.6 million ($AU 4.4 billion).
For Bostonians the years of innumerable controversies have turned the project a cause célèbre and early in March Massachusetts passed new legislation to enable State lawyers to pursue "cost recoveries" dating back 10 years - instead of what had been the statutory limit of six years.
Despite its woes, Big Dig is producing significant advances. It has achieved a world first in tunnel engineering; and encouraged unusually wide public debate on city landscaping. (See: "Beyond Big Dig") The sheer size of the project has made management one of the biggest challenges. It was at the request of the project managers, the Massachusetts Turnpike Authority (MTA), that Big Dig was put under intensive review by two of America's most prestigious independent bodies - the National Academy of Engineering and the US National Research Council.
Their joint report has just been published - along with detailed recommendations of how the project should be brought to completion sometime in 2005. The purpose of the review was not to apportion blame for past mistakes but identify ways in which money might be saved - and the project speedily completed. It is hard to exaggerate the scale of the project. It was originally conceived to improve traffic flow through the city centre - and divert much of the traffic underground.
It was designed to link several major roads and transport hubs and replace a badly deteriorating elevated highway. In total it has involved the construction of 12.5kms of bridges, underground highways (including a tunnel opened in 1995 under Boston Harbour) and ramps.
One example of the challenges faced - and the engineering sophistication employed to meet them - can be found in a contract recently completed by international construction consultants, Mott MacDonald - the same company responsible for the new Maritime Museum at Fremantle. (download the April/May edition of TransScan for more information.)
The company devised a system whereby three full-sized highway tunnels, 100 metres long and each section weighing up to 30,000 tonnes, were slid into position immediately below an operating, commuter railway. Had the company relied on conventional cut-and-cover tunnelling, the railway would have needed "relocation" five times. The tunnels would also have taken an extra two years to build.
"With seven interconnecting rail tracks carrying over 40,000 people a day (the conventional method) was seen as a non-starter from both safety and railway operational points of view," said Alan Powderham, Mott MacDonald's transportation director in a media statement.
But while these particular tunnels saved time, overall Big Dig is running late and the report by the independent review is recommending a number of actions to speed the process. The report says the "biggest boost" to the project would come from "expediting the processing of about 3500 disputed payments to contracts and approved changes to design and construction contracts".
It says this "steadily growing backlog promises more delays and cost overruns if left unresolved". The reviewers says no documented plan exists for dealing with the backlog, each of which has an average age of 600 days and a combined value of $US 230 million.
As a solution, they recommend setting a target date of July 2004 to resolve unsettled claims and immediately paying contractors involved for direct costs from approved changes. Meanwhile the report recommends that with design work done and completion only three years away, the MTA should begin to turn the project organisation from one dominated by consultants to one composed of full-time operations staff.
Although the report's main recommendations aim specifically at Big Dig, it does make some observations that can be applied to other large projects.
"Independent peer review, which provides an outside perspective to identify issues that may have been missed, is often used as a means of quality assurance on complex engineering projects," says the report.
"Truly independent reviews have not been conducted on the Big Dig and at this time, a technical review would be of limited value since most design decisions have been made.
However, with major construction still to be completed, MTA should establish an external, independent peer review program to address technical and management issues until transition to operations and maintenance is completed."
