Big Dig
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Image:Mhs logo.gif- For the Canadian project, see Big Dig (Regina, Saskatchewan).
Big Dig is the unofficial name of the Central Artery/Tunnel Project (CA/T), a megaproject to reroute the Central Artery (Interstate 93), the chief controlled-access highway through the heart of Boston, Massachusetts, into a 3.5 mile (5.6km) tunnel under the city. The project also included the construction of the Ted Williams Tunnel (extending Interstate 90 to Logan International Airport), the Zakim Bunker Hill Bridge over the Charles River, and the Rose Kennedy Greenway in the space vacated by the previous I-93 elevated roadway.
The Big Dig is the most expensive highway project in America.<ref name="The Associated Press">"Review Begins After Big Dig Tunnel Collapse", CNN.com, 2006-07-12. Retrieved on 2006-07-25.</ref> Although the project was estimated at $2.5 billion in 1985, over $14.6 billion had been spent in federal and state tax dollars as of 2006.<ref>Johnson, Glen. "Governor seeks to take control of Big Dig inspections", Boston Globe, 2006-07-13. Retrieved on 2006-07-13.</ref> The project has incurred arrests, escalating costs, leaks, poor execution and use of substandard materials. The Massachusetts Attorney General is demanding contractors refund taxpayers $108 million for "shoddy work."<ref name="Reuters-StateWeighs">"State weighs suing 'Big Dig' contractors", International Herald Tribune, 2006-03-20. Retrieved on 2006-07-17.</ref> The final ramp opened January 13, 2006.
A fatal accident raised safety questions and closed part of the project for most of the summer of 2006. Part of the ceiling collapsed in a tunnel segment under South Boston, connecting I-90 to the Ted Williams Tunnel. The July 11 collapse killed one person and may have contributed to the death of another, a heart-attack victim who died en route to a hospital when his ambulance was caught in the resulting traffic jam.<ref name="BostonHerald=ManDies">"Man dies in tunnel backup", Boston Herald, 2006-07-27. Retrieved on 2006-08-08.</ref> On September 1, 2006, one eastbound lane of the connector tunnel was re-opened to traffic<ref name="MassTurnpike=TurnpikeNews">"Turnpike News", Massachusetts Turnpike Authority. Retrieved on 2006-12-03.</ref>.
The Big Dig was featured in the first season of the program Extreme Engineering.
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[edit] Historical background
Boston's historically tangled streets were laid out long before the advent of the automobile. By mid-20th century, car traffic in the inner city was extremely congested, with north-south trips especially so. Commissioner of Public Works William Callahan advanced plans for an elevated expressway which eventually was constructed (1951-59) between the downtown area and the waterfront. The Central Artery (known officially as the John F. Fitzgerald Expressway) displaced thousands of residents and businesses and physically divided the historical connection between the downtown and market areas and the waterfront. Governor John Volpe interceded in the 1950s to send the last section of the Central Artery underground, through the Dewey Square (or "South Station") Tunnel, but while traffic moved somewhat better the other problems remained.
Built before strict federal Interstate Highway standards were developed during the Eisenhower administration, the expressway was plagued by tight turns, an excessive number of entrances and exits, entrance ramps without merge lanes, and continually escalating vehicular loads. Local businesses again wanted relief, historians sought a reuniting of the waterfront with the city, and nearby residents desired removal of this "Green Monster". (Its matte green paint prompted Thomas Menino to call it Boston’s 'other Green Monster'. The original Green Monster is Fenway Park's left field wall.)<ref>Associated Press. "Boston’s ‘Big Dig’ opens to public", MSNBC, 2003-12-20. Retrieved on 2006-07-18.</ref> M.I.T. engineers Bill Reynolds and (eventual state Secretary of Transportation) Frederick P. Salvucci envisioned moving the whole expressway underground.[citation needed]
[edit] Early planning
The project was conceived in the 1970s by the Boston Transportation Planning Review to replace the rusting elevated six-lane Central Artery. The expressway separated downtown from the waterfront, and was increasingly choked with bumper-to-bumper traffic. Business leaders were more concerned about access to Logan Airport, and pushed instead for a third harbor tunnel. In their second terms as governor and secretary of transportation, respectively, Michael Dukakis and Fred Salvucci, came up with the strategy of tying the two projects together—thereby combining the project that the business community supported with the project that they and the City of Boston supported.[citation needed]
Planning for the Big Dig as a project officially began in 1982, with environmental impact studies starting in 1983. After years of extensive lobbying for federal dollars, a 1987 public works bill appropriating funding for the Big Dig was passed by U.S. Congress, but it was subsequently vetoed by President Ronald Reagan as being too expensive. When Congress overrode his veto, the project had its green light and ground was first broken in 1991.<ref>Dan McNichol and Andy Ryan, The Big Dig. Silver Lining Press, 1991</ref>
[edit] Obstacles
In addition to these political and financial difficulties, the project faced several environmental and engineering obstacles.
The downtown area through which the tunnels were to be dug was largely landfill, and included existing subway lines as well as innumerable pipes and utility lines that would have to be replaced or moved. Tunnel workers encountered many unexpected geological and archaeological barriers, ranging from glacial debris to foundations of buried houses and a number of sunken ships lying within the reclaimed land.
The project received approval from state environmental agencies in 1991, after satisfying concerns including release of toxins by the excavation and the possibility of disrupting the homes of millions of rats, and causing them to roam the streets of Boston in search of new housing. By the time the federal environmental clearances were delivered in 1994, the process had taken some seven years, during which time inflation greatly increased the project's original cost estimates.
Reworking such a busy corridor without seriously restricting traffic flow required a number of state-of-the-art construction techniques. Because the old elevated highway (which remained in operation throughout the construction process) rested on pylons located throughout the designated dig area, engineers first utilized slurry wall techniques to create 120 ft.-deep concrete walls upon which the highway could rest. These concrete walls also stabilized the sides of the site, preventing cave-ins during the excavation process.
Other challenges included an existing subway tunnel crossing the path of the underground highway. In order to build slurry walls past this tunnel, it was necessary to dig beneath the tunnel and build an underground concrete bridge to support the tunnel's weight.
[edit] Construction phase
The Central Artery/Tunnel Project was managed by the Massachusetts Turnpike Authority with design and construction supervised by a joint venture of Bechtel Corporation and Parsons Brinckerhoff. Due to the enormous size of the project—too large for any company to undertake alone—the design and construction of the Big Dig were broken up into dozens of smaller subprojects with well-defined interfaces between contractors. Major heavy-construction contractors on the project included Jay Cashman, Modern Continental, Obayashi Corporation, Perini Corporation, Peter Kiewit Sons' Incorporated, J.F. White, and the Slattery division of Skanska USA. (Of those, Modern Continental was awarded the greatest gross value of contracts, joint ventures included.)
The nature of the Charles River crossing had been a source of major controversy throughout the design phase of the project. Many environmental advocates preferred a river crossing entirely in tunnels, but this, along with 27 other plans, was rejected as too costly. Finally, with a deadline looming to begin construction on a separate project that would connect the Tobin Bridge to the Charles River crossing, Salvucci overrode the objections and chose a variant of the plan known as "Scheme Z". This plan was considered to be reasonably cost-effective, but had the drawback of requiring highway ramps stacked up as high as 100 feet (30 m) immediately adjacent to the Charles River. The city of Cambridge objected to the visual impact of the chosen Charles River crossing design. It sued to revoke the project's environmental certificate and forced the project to redesign the river crossing again. Meanwhile, construction continued on the Tobin Bridge approach. By the time all parties agreed on the I-93 design, construction of the Tobin connector (today known as the "City Square Tunnel" for a Charlestown area it bypasses) was far along, significantly adding to the cost of constructing the U.S. Route 1 interchange and retrofitting the tunnel.
Boston blue clay and other soils extracted from the path of the tunnel were used to cap many local landfills, fill in the Granite Rail Quarry in Quincy, and restore the surface of Spectacle Island in the Boston Harbor Islands National Recreation Area.
The Zakim Bunker Hill Bridge, designed by Swiss designer Christian Menn, is the terminus of the project, connecting the underground highway with I-93 and US 1. The distinctive cable-stayed bridge is supported by two forked towers connected to the span by cables and girders.
The Storrow Drive Connector, a companion bridge to the Zakim, began carrying traffic from I-93 to Storrow Drive in 1999. The project had been under consideration for years, but was opposed by the wealthy residents of the Beacon Hill neighborhood. However, it finally was accepted because it would funnel traffic bound for Storrow Drive and downtown Boston away from the mainline roadway.<ref>Leonard P. Zakim-Bunker Hill Memorial Bridge. BostonRoads.com. Retrieved on 2006-07-18.</ref> The Connector ultimately used a pair of ramps that had been constructed for Interstate 695, enabling the mainline I-93 to carry more traffic that would have used I-695 under the original Master Plan.
When construction began, the project cost, including the Charles River crossing, was estimated at $5.8 billion. Eventual cost overruns were so high that the chairman of the Massachusetts Turnpike Authority, James Kerasiotes, was fired in 2000. His replacement had to commit to an $8.55 billion cap on federal contributions. Total expenses eventually passed $15 billion.
[edit] Current status
On January 17, 2003, the opening ceremony was held for the I-90 Connector Tunnel, extending the Massachusetts Turnpike (Interstate 90) east into the Ted Williams Tunnel, and onwards to Logan Airport. (The Williams tunnel had been completed and in limited use for commercial traffic and high-occupancy vehicles since late 1995.) The westbound lanes opened on the afternoon of January 18 and the eastbound lanes on January 19.
The next phase, moving the elevated Interstate 93 underground, was completed in two stages: northbound lanes opened in March 2003 and southbound lanes (in a temporary configuration) on December 20, 2003. A tunnel underneath Leverett Circle connecting eastbound Storrow Drive to I-93 North and the Tobin Bridge opened December 19, 2004, easing congestion at the circle. All southbound lanes of I-93 opened to traffic on March 5, 2005, including the left lane of the Zakim Bridge, and all of the refurbished Dewey Square Tunnel.
By the end of December 2004, 95% of the Big Dig was completed. Major construction remained on the surface, including construction of final ramp configurations in the North End and in the South Bay interchange, and reconstruction of the surface streets. Many impact-mitigation projects (transit, pedestrian, bicycle, and parks) also remain, but some are in danger of cancellation due to cost overruns on the rest of the project.
The final ramp downtown—exit 20B from I-93 south to Albany Street—opened January 13, 2006.<ref>Ross, Casey. "Hallelujah Hub drivers! Last Big Dig ramp done", Boston Herald, 2006-01-14. Retrieved on 2006-07-18.</ref>
In 2006, the two Interstate 93 tunnels were dedicated as the Thomas P. O'Neill Jr. Tunnel, after the former Democratic speaker of the House of Representatives from Massachusetts who pushed to have the Big Dig funded by the federal government.
On July 11, 2006, the I-90 connector tunnel was closed indefinitely due to an accident. Twelve tons of ceiling concrete in the tunnel collapsed; three tons crushed a car in which a Boston woman was riding as a passenger. She was killed instantly; her husband, who was driving at the time, escaped with only minor injuries. Engineers are in the process of assessing the situation, which may be related to faulty anchor bolts, and making repairs to the materials. The collapse has sparked much debate in the engineering community.<ref>Taurasi, Elizabeth. "Boston’s Big Dig – One of Engineering’s Biggest Mistakes?", Design News, 2006-07-28]. Retrieved on 2006-08-11. See WikiNews article here.</ref>
[edit] Substandard work, criminal misconduct, and collapses
[edit] "Thousands of leaks"
As far back as 2001, Turnpike Authority officials and private contractors knew of thousands of leaks in the ceiling and wall fissures, extensive water damage to steel supports and fireproofing systems, and overloaded drainage systems[1]. A $10 million contract, signed off as a cost overrun, was used to repair these leaks. Many of the leaks were a result of Modern Continental and other subcontractors failing to remove gravel and other debris before pouring concrete. This was not made publicly known to the media, but the MIT engineers (volunteering students and professors) did several precise experiments and figured out a few serious problems of the tunnel. <ref name="evenmorebigleaks">"Report: Even More Big Dig Leaks Found", WCVB-TV, 2004-11-17. Retrieved on 2006-07-18.</ref>
On September 15, 2004, a major leak in the Interstate 93 north tunnel forced the closure of the tunnel while repairs were conducted. This also forced the Turnpike Authority to release information regarding its non-disclosure of prior leaks. A follow-up reported on "extensive" leaks that were more severe than state authorities had previously acknowledged. The report went on to state that the $14.6 billion tunnel system was riddled with more than 400 leaks. A Boston Globe report, however, countered that by stating there were nearly 700 leaks in a single 1000-foot section of tunnel beneath South Station. Turnpike officials also stated that the number of leaks being investigated was down from 1000 to 500. <ref name="evenmorebigleaks" />
[edit] Substandard materials
On August 11, 2005, it was announced that the Massachusetts State Police searched the offices of the Big Dig's largest concrete supplier in June and found evidence of faked records that hid the poor quality of concrete delivered for the highway project. However, it is not believed that the low-quality concrete is connected to the hundreds of leaks discovered in the tunnels that take vehicles under Boston[citation needed].
On March 19, 2006, the International Herald Tribune reported that Massachusetts Attorney General Tom Reilly plans to sue Bechtel/Parsons Brinckerhoff and other companies if the two sides do not reach an agreement over 200 complaints of poor work in the construction of a highway system under the center of Boston, the Boston Globe reported Saturday. Reilly was said to be seeking $67 million from Bechtel and $41 million from other companies."<ref name="Reuters-StateWeighs"/>
[edit] Criminal misconduct
On May 4, 2006, six current or former employees from the concrete supplier Aggregate Industries Inc. were arrested and charged for falsifying records regarding the poor quality concrete.
On May 5, 2006, due to the controversy, Massachusetts Governor Mitt Romney announced he would return $3,900 in political contributions from employees of Aggregate Industries.<ref>"Romney to return contributions from Big Dig concrete workers", WPRI.</ref>
[edit] Big Dig tunnel ceiling collapse
At approximately 11:00 p.m. on Monday, July 10, 2006, four sections of ceiling tiles fell to the roadway on eastbound I-90, along a section of connector tunnel that leads to the Ted Williams Tunnel in South Boston. The concrete panel tiles, each weighing around three tons, crushed a car passing underneath, killing the passenger, 38-year-old Milena Del Valle, and slightly injuring the driver, Angel Del Valle.
[edit] References
[edit] See also
- Dublin Port Tunnel - Similar project in Dublin, Ireland with similar problems.
- Massachusetts Turnpike
- Interstate 90
- Interstate 93
- Ted Williams Tunnel
- Sumner Tunnel
- Callahan Tunnel
- Leonard P. Zakim Bunker Hill Bridge
- Conservation Law Foundation
- MBTA
- Tip O'Neill
[edit] External links
- Powell, Michael, "Boston's Big Dig Awash in Troubles", Washington Post, 2004-11-19, Retrieved on 2006-08-09.
- Official site
- Project map
- Boston CA/T Project History at MIT Rotch Library
- Steve Anderson's BostonRoads.com
- PBS.org – Central Arteryfr:Big Dig
