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Home , Big Dig, Central Artery, Dewey Square, Dewey Square Tunnel, Ted Williams Tunnel

PUBLISHED BY THE AMERICAN COUNCIL OF ENGINEERING COMPANIES JULY/AUGUST 2007

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Reprinted with permission of the American Council of Engineering Companies (ACEC), www.acec.org, in cooperation with the American Council of Engineering Companies of (ACEC/MA), www.acecma.org. How the Big Dig Is Transforming

Fifteen-year project is considered one of the most innovative engineering feats in U.S. history BostonSomething had to be done. The main artery and hen the that knifed its secondary tributaries were hemorrhaging, bleed- through the center of downtown ing the life out of the city’s heart—economically and Boston opened in 1959, the from a quality-of-life perspective. But all that began to change in 1991 when con- could adequately handle struction crews broke ground on the Central Artery/ some 75,000 per day. Through Project, commonly known as the Big Dig. the years, the number skyrocketed to upwards of The surgery was an overwhelming success. Today W Boston’s traffic flows smoothly, neighborhoods are 200,000 daily vehicles, creating one of the most once again connected and the economic impact of congested highways in the country. n Traffic snarled the project has pumped new life into the heart of downtown. for 10 hours per day and the accident rate surged to The scope of the project is nothing less than four times the national average for urban interstates. breathtaking. The Big Dig is larger in size than the Panama Canal; engineers had to support existing Similar problems beset the two under Boston high-rise buildings, subways and other infrastruc- Harbor. Moreover, the Central Artery displaced ture while constructing tunnels and managing traf- 20,000 residents when it was built, cutting off fic flow for more than 200,000 motorists a day. Along the way, project engineers faced formidable Boston’s North End and waterfront neighborhoods challenges. For example, Boston’s weak soil couldn’t from downtown. n Worse, projections forecast that by support a tunnel, and engineers had to use construc- tion methods that had never before been attempted. 2010, stop-and-go traffic jams would stretch up to 16 Although the Big Dig suffered many of the cost hours a day. and political problems associated with modern-day

12 ENGINEERING INC. July / AuGust 2007 Big Dig Engineering Firsts

n The world’s widest How the Big Dig Is Transforming cable-stayed bridge, the Leonard P. Zakim Bunker The leonard P. Zakim Bunker Hill Bridge is the Hill Bridge, carries 10 centerpiece of the Big dig. lanes of traffic and can withstand 400 mph winds.

n The deepest underwater tunnel in North America. The Tunnel in reaches nearly 100 feet below the surface of .

n An innovative ground- freezing 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 by Samuel Greengard degrees Fahrenheit.

n The most extensive after geotechnical DARREN MCCOLLESTER/GETTy IMAGES MCCOLLESTER/GETTy DARREN Bostonmegaprojects—the price tag swelled from $2.6 bil- Before investigation, testing and monitoring program lion to more than $14.6 billion—it has succeeded in North America in easing Boston’s famous traffic tie-ups. prepared the way for According to the Author- excavation, tunneling and ity (MTA), the project has trimmed the average trip construction. 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 n One of the largest added 300 acres of new parks and plazas. “The proj- tunnel ventilation ect has made Boston a more viable city with a great systems in the world future,” states Richard Dimino, president and CEO used 151 infrared sensors of A Better City, an organization that promotes controlling 140 fans used to blow fresh air in and business interests in Boston. exhaust fumes out. MASSACHUSETTS TURNPIKE MASSACHUSETTS AUTHORITY Clearing Congestion 1989: The elevated Central artery in experienced nine hours of gridlock a day. The Big Dig is a story of vision, innovation and n The largest use of persistence. The genesis of the project dates to gasoline, road repairs and related costs. “It was clear modules in the early 1980s. At the time, Boston faced near- that something had to be done,” Dimino recalls. North America allowed gridlock traffic and a realization that the problem Unfortunately, Boston lacked space to widen its crews to conduct was only going to get worse. A mile-long stretch central highways or build new expressways through excavation work within a of raised highway included 27 on-ramps and off- the city. Compounding matters, most of the confined space without ramps, which contributed to serious slowdowns city’s residents already considered the old Central disrupting transportation and dangerous driving conditions and would even- Artery—a.k.a. the Green Monster—an eyesore and systems directly above. tually lead to $500 million a year in additional ongoing problem. Its construction cut off Boston’s

July / AuGust 2007 ENGINEERING INC. 13 Twelve steel binocular immersed tubes, each the The Timeline size of a football field, make up the that crosses Boston Harbor. 1982: Work begins on Final Environmental Impact State- ment/Report (FEIS/R).

1985: FEIS/R filed and approved in early 1986.

1986: /Parsons Brinckerhoff begins work as management consultant.

1987: Congress approves funding and scope of proj- ect. Building acquisition and business relocation process begins; no private homes are taken.

1988: Final design process under way. Exploratory archaeology begins.

1989: Preliminary/final design and environmental review continue.

1990: Congress allocates $755 million to project.

1991: Federal Highway Administration issues Record of Decision, the construction go-ahead. Final FEIS/R approved. Construc- tion contracts begin to be advertised and awarded. Construction begins on Ted Williams Tunnel and Haul Road. Cars and trucks travel north through the new I-93 tunnel. 1992: More than $1 billion in design and construction contracts under way. Dredg- North End and waterfront neighborhoods from methods, along with equal doses of creativity and ing and blasting for the Ted downtown, forever changing the look of the city persistence. Williams Tunnel continues. and, many contend, damaging its economy. “The Big Dig harnessed some of the best tech- Downtown utility relocation to clear path for Central The idea of tunneling under the city and its nical minds in the industry and confronted some Artery tunnel construction waterfront grew out of the realization that there begins. Archaeologists find wasn’t a more practical way to solve Boston’s trans- emoving the raised roadway 17th- and 18th-century arti- facts at a North End dig. portation problems. Fred Salvucci, then secretary Rhas reinvented and re-knitted of transportation for the Commonwealth of Massa- the city. It has helped create an 1993: South Boston Haul chusetts and now a senior lecturer and researcher at Road opens. All 12 sections of the Ted Williams Tunnel the Massachusetts Institute of Technology, believed attractive urban environment…” are placed and connected on it was absurd to “simply rebuild a 50-year-old Michael Bertoulin harbor floor. mistake so that it could hang around for another Parsons Brinckerhoff 1994: Cross- 50 years, polluting and obstructing the economic ing revised design and growth of the city.” He also recognized that total related FSEIS/R approved. closure of existing roadways was not an option. New set of loop ramps open in Charlestown. After studying the city’s transportation problems in the early 1980s, traffic planners recommended a 1995: Ted Williams Tunnel $2.6 billion initiative that would ultimately grow opens to commercial traffic. into a comprehensive quilt of 140 construction 1996: Downtown slurry projects. Construction would span more than a work under way for I-93 decade and redefine modern highway engineering. tunnels. Urban planners and engineers could not have fore- 1997: Overall utility work 80 seen what a complicated and challenging project percent complete. the Big Dig, approved in 1987, would become. It would require new and untested engineering

14 ENGINEERING INC. July / AuGust 2007 he project has made Boston 1998: Peak construction years begin. Construction ta more viable city with a begins on the Charles great future.” River Crossing. of the most difficult conditions highway engineers richard diMino could ever face,” explains Michael Bertoulin, vice 1999: Overall construction a Better city 50 percent complete. New president of Parsons Brinckerhoff, part of the Broadway Bridge opens. construction management team on the Big Dig. Connector “The challenges associated with keeping the city Bridge opens. running during the height of construction were 2000: Nearly 5,000 enormous.” workers employed on the Big Dig.

A UTHORITY Deep Thinking 2001: Overall construction The first phase of the project involved tunneling 70 percent complete. URNPIKE under Boston Harbor using the immersed tube 2002: Leonard P. Zakim tunnel (ITT) method. In 1991, a dredger known Bunker Hill Bridge as the “Super Scoop” began dredging 900,000 completed.

MASSACHUSETTS T MASSACHUSETTS cubic yards of earth. This enabled work crews 2003: I-90 Connector to begin laying steel ITT sections across the har- the 33-ton sections in 1995. By December of that from South Boston to bor. Each of the ITTs consisted of a 15,000-ton year, the newly christened Ted Williams Tunnel Rt. 1A in East Boston opens in January. I-93 composite structure composed primarily of con- opened on budget and on schedule. Northbound opens in crete and a pair of 40-foot steel tubes joined side But the Big Dig had only just begun. In order to March. I-93 Southbound by side and extending 330 feet. By 1992, the connect the tunnel to I-90, engineers had to build opens in December. 12 tunnel sections—built by Maryland-based another tunnel under Boston’s 400-foot-wide Fort 2004: Dismantling of the Bethlehem Shipbuilding—began arriving at the Point Channel. The eight-lane highway would elevated Central Artery site. Crews then added concrete to transform the have to cross over a subway line, run adjacent to a (I-93). Opening of the tunnel from Storrow steel hulks into structures that would serve as the manufacturing plant and large post office and run Drive to Leverett Circle highway’s foundation. beneath commuter rail lines. To extend I-90 under Connector, which provides In 1993, a catamaran barge began towing the the tracks and across the channel, engineers were access to I-93 North and . ETTy IMAGES tunnel sections into position. Each of the tubes forced to push the limits of existing technologies. /G had to be lowered within a fraction of an inch The process involved a combination of imaginative 2005: Full opening of from their designated location in order to ensure concrete box ITTs, massive ground modification I-93 South. The opening of the completely renovated a watertight seal. Workers used global positioning and “jacked” highway tunnel boxes underneath an Tunnel, DARREN McCOLLESTER DARREN devices and lasers to position pieces of the tun- operating rail corridor. including new exit and nel within the murky waters of Boston Harbor. Engineers turned to soil mixing—a Japanese entrance ramps. Opening of the two cantilevered Working 100 feet below the surface—the Big Dig technique—to modify the pudding-like soil on lanes on Leonard P. Zakim was the deepest tunneling project in the history the bank of the . Using heavy Bunker Hill Bridge. Opening of North America—workers finished connecting blades and rotors, construction workers drilled of permanent ramps and roadways at I-90/I-93 down approximately 130 feet and mixed in cement interchange and in t is a terrific example of to create a material that would support 300 to other areas. Iengineering excellence and 1,000 pounds per square inch (PSI). After solidify- ing an area and creating a mass gravity wall, exca- 2006: Reached substantial innovation. It will be a case study completion of the Central vation commenced adjacent to existing commuter Artery/Tunnel Project in for building large public projects.” rail lines at the channel edge. The area became the January. Spectacle Island aBBie r. GoodMan interface between the ITTs and jacked tunnels. Park opens to the public. acec/Massachusetts However, low bridges in the channel prevented 2007: Restoration of crews from building the ITTs off-site. Instead, Boston city streets. Continued construction engineers created a 60-foot-deep and 1,000-foot- of the long dry dock, otherwise known as a casting basin. Greenway and other The basin held six different concrete sections dur- parks. Construction on development parcels ing construction. continue after the The challenges didn’t stop there. Crews had to Central Artery/Tunnel float the 27-foot-high sections (which measured Project is finished. up to 414 feet long and 174 feet wide) into place. Construction teams also couldn’t build all the SOURCE: Massachusetts Turnpike Authority. structures at the same time—meaning the basin had to be filled and drained more than once. Two of the sections served as the foundation for venti- lation structures on their roof—thus making the

July / AuGust 2007 ENGINEERING INC. 15 KEy PLAyERS FRed SalvuCCI By the an engineer and former Numbers Massachusetts transportation secretary (1983–1990), he is n Amount of dirt process of transporting them, and balancing their excavated: 15 million credited with first envisioning cubic tons. weight within the water, even more complex. the concept of the Big dig Using remote control cameras, engineers posi- and generating the project’s n Concrete used to replace tioned the pieces and connected them like giant initial financial and political the dirt: 3.8 million cubic feet. Lego blocks. support. Constructing the last link between the ITT and Sally PeRRIn n Steel used: 26,000 I-90 created another challenge. Engineers had to Former deputy project linear feet. dig under commuter rail lines carrying more than manager for the Bechtel/ n Traffic management 150 trains and 100,000 passengers a day, without Parsons Brinckerhoff team, system: 400 video cameras, disrupting the tracks. Once again, workers faced the 130 electronic message she oversaw environmental signs, 30 infrared height problem of soft soil that couldn’t support tunneling. mitigation, real estate and detectors, six emergency Any attempt to remove the soft soil under the tracks traffic management as they response systems. risked derailing the entire project. That’s when one prepared for construction. n Reduction in contractor proposed a new and radical solution: due to central artery Freeze the soil during the tunneling process using project: 12 percent citywide. 2,000 pipes located eight feet apart, each filled with a JoHn Kennedy brine refrigerant solution chilled to minus 30 degrees Senior principal at vanasse n Maximum number of Hangen Brustlin, Inc., construction workers Fahrenheit. “It was like creating a manmade per- on project: approximately mafrost,” Bertoulin says. Workers mined 18 inches he designed the traffic 5,000. management plan that into the frozen soil, creating a void using the tunnel- maintained safe and efficient n Number of construction jacking process. The tunnel jacking required 10,000 traffic operations during the contracts executed: 109. PSI to move the 35,000-ton sections at a rate of 15-year Big dig construction n Underground utilities three feet per day until they were in place. The pro- period. relocated: 29 miles of cess took three years to complete, but left the struc- gas, electric, water, sewer, tures on the surface untouched. Paul HaRRIngTon telephone and other lines director of structural division at managed and maintained by In September 2001, a massive leak occurred in 31 companies. the section where the land and sea tunnels met. Fay Spofford & Thorndike, Inc., Rapidly rising water inundated expensive cranes he developed the underpinning n Deepest point: 120 feet and other equipment and made the tunnel impass- (foundation support) system at Dewey Square, where it that allowed tunnel construction passes beneath the able. Although crews began working on the prob- Red Line subway. lem immediately, it took divers nearly eight weeks to proceed without affecting to identify and plug the leak. By then, the opening existing transit/rail systems or n New parkland: 300 acres surface structures. (27 acres reclaimed from of the tunnel was delayed by four months. the ). Sena KuMaRaSena Driving Results n Toxic contaminants HnTB associate vice hauled away: 435,000 cubic The final piece of the project was the engineer- president, he served as yards of soil and other debris. ing of the tunnel beneath I-93. To clear space for project engineer and project the underground highway, engineers had to build manager during the design The old elevated High Bridge corridors to relocate pipes, cables and other infra- and construction of the over the Charles River is structure that fills virtually every square inch of leonard P. Zakim Bunker Hill demolished in early 2004. subterranean Boston. At one point, they had to dig Bridge, the widest cable- underneath three levels of subterranean transporta- stayed bridge in the world.

A UTHORITY tion systems—subway lines, heavy rail and a bus station—and create a tunnel space only 36 inches been attempted on such a large scale.

URNPIKE beneath the subway. Project planners also recognized the need to “Essentially, we had to create a parallel set of replace a deteriorating three-lane double-decker walls with huge crossbeams beneath the exist- bridge over the Charles River used to connect ing raised structure in order to build the tunnel. the tunnel to the interstate. Further complicating MASSACHUSETTS T MASSACHUSETTS The ground had to support both the existing the project, engineers decided it was necessary to steel and concrete structure and the tunnel box,” build around the existing bridge structure so that says Frank Leathers, a geotechnical engineer traffic continued to flow during construction. and president of GEI Consultants, Inc., which Today, the $100 million cable-stayed Leonard designed one section of the slurry walls for the P. Zakim Bunker Hill Bridge, the widest asym- project. Prior to the Big Dig, Leathers says, the metrical bridge ever built, carries 10 lanes of slurry wall module building method had never traffic—eight through the legs of twin towers

16 ENGINEERING INC. July / AuGust 2007 KEy PLAyERS

Before A UTHORITY URNPIKE

after MASSACHUSETTS T MASSACHUSETTS once a mass of elevated highway ramps, north On Jan. 18, 2003, officials raised the for five months while workers replaced the end Park, part of Boston’s Rose Fitzgerald sign on I-90 and opened the last section panel’s anchor. Later, Thomas F. Reilly, Kennedy greenway, will open in spring 2008 (top of the 3,462-mile link to . A year attorney general for Massachusetts, filed right). a series of 14 parks will cut through the later, workers dismantled the old I-93 15 lawsuits against firms that he accused city from Causeway to Kneeland Streets (above). structure and began replacing it with 300 of negligence in the ceiling collapse. acres of parks and plazas. “Removing the Nevertheless, the Big Dig left a supporting the bridge and two cantile- raised roadway has reinvented and re- remarkable imprint on Boston. With 7.8 vered on the east side. It is designed to knitted the city,” Bertoulin says. “It has miles of highway and 161 total lanes, withstand 400 mph winds and a magni- helped create an attractive urban envi- it has greatly reduced traffic, accidents tude 7.9 earthquake. ronment that otherwise wouldn’t have and air pollution. A new park—the Throughout the Big Dig, engineers had been possible.” Rose Kennedy Greenway—will accom- to keep cars flowing. “It was essential to modate joggers, picnickers, workers on understand how every aspect of the project Leaving a Legacy lunch breaks, local residents walking would affect traffic patterns and driving Though the Big Dig has distinguished dogs, and children at play. And the Bos- conditions,” explains John J. Kennedy, a itself as an engineering marvel on par with ton waterfront, now reconnected to the traffic consultant with Watertown, Mass.- the Panama Canal, Europe’s Chunnel and city, is enjoying an economic boom. based Vanasse Hangen Brustlin, Inc. “We the Hoover Dam, its accomplishments are “It is a terrific example of engineering had to make sure that total coordination not without controversy. At $14.6 billion, excellence and innovation. It will be a existed among various contractors and the Big Dig is the most expensive highway case study for building large public proj- government agencies.” Engineers rerouted project in history and its eventual price ects,” says Abbie R. Goodman, executive traffic daily and, almost without excep- tag—more than $12 billion above the ini- director of ACEC/Massachusetts. tion, improved traffic flow during the con- tial estimate—has left some citizens and The legacy extends far beyond Bos- struction phase, he recalls. government officials angry and dissatis- ton. “Many of the design and engineer- At its peak, the Big Dig employed fied. The Massachusetts Turnpike Author- ing methods used for the Big Dig have nearly 5,000 construction workers. The ity filed a $146 million breach-of-contract been picked up and applied to other management team of Bechtel Corp. and lawsuit in 2004 over cost increases and projects around the world,” Bertoulin Parsons Brinckerhoff oversaw 38 design other lingering issues, including outstand- explains. And although some techniques contracts and 119 construction contracts ing legal and insurance claims, with the are so specialized that they haven’t involving 109 companies. “It was a very Commonwealth of Massachusetts. ACEC/ yet made their way into mainstream schedule-driven project that required tre- Massachusetts is now sorting through the engineering projects, the innovation mendous synchronization of people and mess. “It’s a complex matter that will take and lessons learned have proved invalu- resources,” explains William J. Rizzo, years to resolve,” Leathers says. able. “That’s the nature of engineer- former CEO and president of Tetra Tech The project also endured its share of ing and construction,” Bertoulin says. Rizzo, which handled the engineering tragedies. Sadly, four workers died while “Every project draws on the knowledge for two interchanges along I-93. “We building the tunnels and infrastructure. gained from previous projects, and every- had people from different companies— In July 2006, a motorist passing through one benefits.” n with entirely different cultures—working the I-90 connector tunnel was killed after together [in a joint venture] to achieve a bolts failed and a 12-ton concrete slab fell Samuel Greengard is a business and technol- mutual goal.” atop her vehicle. The tunnel was closed ogy writer based in West Linn, Ore.

July / AuGust 2007 ENGINEERING INC. 17