Engineering Inc. - July/August 2007 - (Page 13)

Transforming The Leonard P. Zakim Bunker Hill Bridge is the centerpiece of the Big Dig. by Samuel Greengard on After Massachusetts turnpike authority Big Dig Engineering Firsts n The world’s widest cable-stayed bridge, the Leonard P. Zakim Bunker Hill Bridge, carries 10 lanes of traffic and can withstand 400 mph winds. n The deepest underwater tunnel in North America. The Ted Williams Tunnel in East Boston reaches nearly 100 feet below the surface of Boston Harbor. DArrEN MccOLLESTEr/GETTy IMAGES n An innovative groundfreezing technique stabilized Boston’s weak soil during construction. Approximately 2,000 pipes eight feet apart, were filled with a saltwater coolant solution chilled to minus 30 degrees Fahrenheit. megaprojects—the price tag swelled from $2.6 billion to more than $14.6 billion—it has succeeded in easing Boston’s famous traffic tie-ups. According to the Massachusetts Turnpike Authority (MTA), the project has trimmed the average trip through the center of Boston from 19.5 minutes to 2.8 minutes, reduced rush-hour backups from 10 hours per day to a couple of hours per day and added 300 acres of new parks and plazas. “The project has made Boston a more viable city with a great future,” states Richard Dimino, president and CEO of A Better City, an organization that promotes business interests in Boston. Clearing Congestion Before n The most extensive geotechnical investigation, testing and monitoring program in North America prepared the way for excavation, tunneling and construction. n One of the largest tunnel ventilation systems in the world used 151 infrared sensors controlling 140 fans used to blow fresh air in and exhaust fumes out. The Big Dig is a story of vision, innovation and persistence. The genesis of the project dates to the early 1980s. At the time, Boston faced neargridlock traffic and a realization that the problem was only going to get worse. A mile-long stretch of raised highway included 27 on-ramps and offramps, which contributed to serious slowdowns and dangerous driving conditions and would eventually lead to $500 million a year in additional 1989: The elevated Central Artery in downtown Boston experienced nine hours of gridlock a day. gasoline, road repairs and related costs. “It was clear that something had to be done,” Dimino recalls. Unfortunately, Boston lacked space to widen its central highways or build new expressways through the city. Compounding matters, most of the city’s residents already considered the old Central Artery—a.k.a. the Green Monster—an eyesore and ongoing problem. Its construction cut off Boston’s n The largest use of slurry wall modules in North America allowed crews to conduct excavation work within a confined space without disrupting transportation systems directly above. July / AuGust 2007 ENGINEERING INC. 13

Table of Contents for the Digital Edition of Engineering Inc. - July/August 2007

Call for Entries
Contents
From ACEC to You
News & Notes
Market Watch
Legislative Action
The Big Dig
Risky Engineering
2007 Professional Liability Survey
Institute For Business Management Fall 2007 Course Catalog
Roadside Technology
2007 Convention Wrap-Up
2007-2008 Excom
2007 Fall Conference Primer
Business Insights
Technology
Members in the News
One on One

Engineering Inc. - July/August 2007