Big Dig
The Big Dig (roughly: "The Great Ditch") was a major urban development project in Boston , with which the most-used urban freeway in the city, the John F. Fitzgerald Expressway , was laid in a tunnel. The lowering of the central city motorway, officially known as the Central Artery / Tunnel Project (CA / T) and planned and built since 1982, combined with a new underground crossing of the Charles River, was one of the most complex civil engineering projects in the world.
At the height of construction, 5,000 workers were involved in the Central Artery project. In 2004 the stilt motorway was dismantled. A technocratic compromise was or is being established - with over 80 percent federal funding. The lowered urban motorway is now designed for 240,000 vehicles per day, the surface design (which is still in progress) is a little less green than ecological citizens' initiatives had imagined. However, the urbanistic effects are considered positive. In particular, the isolation of Boston from its waterfront , which has been successfully revitalized in recent decades, has been eliminated. According to a recent announcement from the Massachusetts Turnpike Authority , the total costs amount to $ 14.6 billion, more than five times the originally targeted $ 2.6 billion. The open spaces gained by lowering the urban motorway will be around eleven hectares, and the building will reduce Boston’s carbon dioxide pollution by around twelve percent.
Historical background
Boston's branching streets were laid out long before the automobile was born . In the middle of the 20th century, the masses of cars in the streets of the city center regularly brought traffic to a standstill. Public works commissioner William Callahan put forward plans for an elevated highway that would eventually be built between the city center and the waterfront from 1951 to 1959.
The Central Artery was built before the stringent Interstate Highway standards were developed under the Eisenhower administration . As a result, the motorway was marked by sharp turns, an excessive number of entrances and exits, and entrances with no lane to classify.
Early planning
Lowering the six-lane Central Artery has been the subject of intense discussion since the 1970s. The elevated road , designed for a capacity of 75,000 cars per day, was hopelessly overloaded with over 200,000 cars per day, and the steel girder construction showed significant signs of fatigue. A gradual renovation of the existing structure and the associated traffic obstructions would have caused total traffic chaos in downtown Boston for years.
Furthermore, the negative urban effects of a stilted motorway, especially in potentially high-priced, inner-city real estate locations, suggested a tunnel solution . With the redesign of the "main artery" of private transport, environmental activists linked the hope of a renewed, greener inner city. The Boston architects, on the other hand, hoped for more building contracts in the central locations that were now vacant. A direct motorway link under the river to the city's airport was also to be created.
Preliminary planning
Planning for the project officially began in 1982, the environmental impact studies in 1983. After years of extensive solicitation for federal funds, a funding plan passed the US Congress in 1987 , but this was rejected by President Ronald Reagan as being too expensive. When Congress lifted Reagan's veto, the project was given the go-ahead and the groundbreaking groundbreaking in 1991 was laid.
Obstacles
In addition to financial difficulties, the project faced several environmental and engineering barriers. For example, the bottom of the inner city through which the tunnels were to be dug consists largely of land fill. In addition, an underground railway is being crossed and countless pipes and shafts had to be replaced or moved.
Workers encountered many unexpected geological and archaeological barriers, from ice rubble to the foundations of buried houses to several sunken ships lying in the construction zone.
Only with the help of highly developed construction techniques was it possible to build such an important traffic axis without excessively restricting the flow of traffic. So were diaphragm walls founded in over 36 meters depth, which intercepted the masts of the existing motorway route during the construction period and stabilized the entire excavation.
Another obstacle was the Südbahnhof, whose seven tracks are used by 400 trains and over 40,000 commuters every day. Instead of swiveling the tracks several times, as initially planned, a special support structure was built here too, under which the motorway tunnel was dug. In addition, the ground around the construction pit was frozen in order to further increase the stability.
An underground concrete bridge was built for the crossing underground tunnel, which was built on the foundation of the building pit and thus supported and stabilized it.
Construction phase
The main project of the Central Artery Tunnel project was directed in design and construction by the Massachusetts Turnpike Authority and monitored by a joint venture of the Bechtel Corporation and Parsons Brinckerhoff . Because of the enormous scope of the project, which far exceeded the capabilities of a single company, the Big Dig was split into dozens of smaller sub-projects and distributed among various contractors.
The main contractors for the project were Jay Cashman , Modern Continental , Obayashi Corporation , Perini Corporation , Peter Kiewit Sons' Incorporated , JF White and the Slattery division of Skanska USA. Overall, Modern Continental received the most contracts, including joint ventures.
One of the most contentious points of the overall project was the crossing of the Charles River. Environmentalists in particular called for a completely subterranean route, but this was rejected as too costly. When the deadline for the start of construction of the connection between the Tobin Bridge and the Charles River Crossing was getting closer and closer, Salvucci ignored the objections and chose a variant of the plan later known as "Scheme Z". This seemed relatively cost-effective, but it meant that highway ramps next to the Charles River would rise 30 meters in height. The city of Cambridge protested against this degradation of the landscape and filed a lawsuit to withdraw the project's environmental certificate. The entire river crossing then had to be re-planned while the feeder to the Tobin Bridge was already under construction. The plan, which was finally agreed, then relocated this section of the route in a tunnel (the so-called "City Square Tunnel" after the name of the square it crosses under). This change in the connection to US Route 1 and the changes to the existing tunnels increased costs considerably.
The blue clay minerals and other soils removed from the tunnels were used to cover many local landfills, replenish the granite rail quarry in Quincy , and restore the surface of Spectacle Island in Boston Harbor Islands National Park .
The Leonard P. Zakim Bunker Hill Memorial Bridge , designed by the Swiss civil engineer Christian Menn , finally marked the end of the project to connect the underground city motorway with I-93 and US 1. The distinctive cable-stayed bridge is supported by two fork-shaped connected pylons, to which the cables and track girders are attached.
In 1999, the Leverett Circle connection , a sister bridge to the Zakim Bridge, was opened for traffic from the I-93 to Storrow Drive. This project was also planned for many years, but was fought for a long time by the wealthy residents of Beacon Hill. That resistance eventually crumbled as it was the only way to channel traffic to Storrow Drive and downtown Boston and divert it away from the inner city streets. Two ramps originally intended for Interstate 695 could be used for the connection. This increased the capacity of the I-93, which could now also accommodate the traffic that would have been carried over the I-695 according to the original plans.
At the start of construction, the cost of the project, including the Charles River crossing, was estimated at US $ 5.8 billion. Even during the construction phase, however, the cost overruns were so high that the chairman of the Massachusetts Turnpike Authority, James Kerasiotes, was dismissed in 2000. His successor had to commit to a limit of US $ 8.55 billion. The total cost eventually came to $ 15 billion.
Final phase
January 17, 2003 marked the opening of the I-90 interconnecting tunnel , extending the Massachusetts Turnpike ( Interstate 90 ) east into the Ted Williams Tunnel , and forward to Logan Airport . (The Williams Tunnel had been completed since the end of 1995 and was released for limited use for commercial traffic and for high-occupancy vehicles (vehicles with at least two people).) The westward direction opened on the afternoon of January 18th, the eastward one leading on January 19th.
The next phase of underground interstate 93 was carried out in two stages. The northbound lanes were released in March 2003, the southbound lanes in a provisional arrangement on December 20, 2003. A tunnel under Leverett Circle, which connects eastbound Storrow Drive with Interstate 93 to the north and the Tobin Bridge , was built Opened on December 19, 2004 to reduce traffic jams around the roundabout. The last southward lanes of Interstate 93 including the left lane of the Zakim Bridge and the repaired Dewey Square Tunnel were opened to traffic on March 5, 2005.
In September 2004 there was a water ingress in the north tunnel, as a result of which the tunnel had to be temporarily closed. As part of the subsequent investigation, the project management admitted that the tunnel had over 1000 leaks. New reports showed that even in March 2007 7.2 million liters of water were being pumped out of the tunnel every month. The leaks are partly due to inferior concrete and cracks in the concrete and were the reason for a claim for damages against several of the construction companies involved.
On July 10, 2006, two ceiling tiles with a total weight of 2.6 tons fell on a car driving in the tunnel, fatally injuring 38-year-old passenger Milena Del Valle. The collapse took place in the Interstate 90 -East tunnel at the level of D-Street. As a result of the collapse, all ceiling tiles of the same design in the I-90-East and I-90-West tunnels were removed and the I-90 tunnel was closed for several months. Exactly one year later, the NTSB published its report, in which it was established that the use of inferior epoxy resin to bond the ceiling bolts had caused the accident and that the construction companies involved had been negligent. The state of Massachusetts offered the construction consortium Bechtel Parsons-Brinckerhoff on July 14, 2007 a settlement that would be waived against a payment of 1 billion dollars from a lawsuit. This offer was heavily criticized by the media, since in the event of a trial, the penalty for Bechtel Parsons-Brinckerhoff should be significantly higher.
Following extensive inspections and repairs, the Interstate 90 east and west routes reopened in early January 2007.
Extensions
The project also includes the construction of the Ted Williams Tunnel as an extension of Interstate 90 to Logan International Airport , the Zakim Bunker Hill Bridge over the Charles River and the Rose Kennedy Greenway Park on the site of the previous freeway. Originally, the plan also included a rail link , known as the North-South Rail Link , between the two main stations in Boston.
costs
The Big Dig is the most expensive road construction project in the United States . Estimated initially at $ 2.8 billion in 1985, the total cost to the end of 2006 was more than 14.6 billion, funded by federal and Massachusetts taxpayers' money . During the course of the project, there were criminal investigations, skyrocketing costs, poor management and the use of substandard materials. The Massachusetts Attorney General is considering $ 108 million claims for damages against several construction companies to compensate the state for the bad work.
Comparable projects
literature
- Dan McNichol: The Big Dig . Silver Lining Books, 2001, ISBN 0-7607-2307-9 .
- Peter Vanderwarker: The Big Dig . Reshaping an American City. Little Brown and Company, Vienna 2001, ISBN 0-316-60598-0 .
- National Academy of Science (Ed.): Completing the Big Dig . Managing the Final Stages of Boston's Central Artery / Tunnel Project. Natl Academy Pr, 2003, ISBN 0-309-08887-9 .
- Robert Schediwy: City Pictures . Reflections on the change in architecture and urbanism. LIT, Vienna 2005, ISBN 3-8258-7755-8 , p. 47-49 .
- Orikaye G. Brown-West: IN DEFENSE OF THE BIG DIG: How Politics Affected the Planning, Design and Construction of the Boston Central Artery / Tunnel Project , Lulu.com, 2007 (English)
