Central Artery pumps new life into Boston
In baseball, Boston is known for the Green Monster, the 60-foot-high left field wall at Fenway Park that has frustrated many a hitter. But the city has another Green Monster: the green steel elevated section of Interstate 93 that runs through the city’s heart. That Green Monster has frustrated many a commuter.
In the 1980s, in an attempt to reknit divided neighborhoods and ease congestion through downtown, Boston began reconstructing that section of I-93, which is known as the Central Artery. When it is completed five years from now, the project will streamline traffic flow within and around the city; relieve congestion; reduce accidents; dramatically improve air quality; reconnect fractured neighborhoods; provide acres of open space for parks and gardens; and allow for additional downtown development.
Moreover, given that Boston’s traffic situation does not just affect Boston, the project is expected to enhance neighboring New England communities. “Boston is the commercial hub of the entire New England area, so a considerable number of major highways converge on the city,” says Andy Paven, director of communications for the Central Artery/Third Harbor Tunnel (CA/T) Project. “Consequently, I-93 through the city has evolved into an essential part of the transportation system for all of New England. There was little choice but to aggressively attack this situation to protect the commercial future of New England.”
The history The Central Artery, part of an overcrowded and outdated downtown thoroughfare system, has helped give Boston a reputation as one of the nation’s most congested cities. Built in the late 1950s as a six-lane interstate route, I-93 runs north/south through much of the central city.
One of the first highways in the national interstate system, I-93 initially was part of a plan involving construction of three new highways. However, a shift in state priorities toward mass transportation resulted in cancellation of the other two projects. Now, with no curb or breakdown lanes and 27 access ramps through downtown, I-93 handles a daily traffic load of more than 190,000 vehicles (compared to 75,000 when it opened in 1959). The traffic problem is exacerbated by the fact that the Massachusetts Turnpike ends abruptly at its juncture with I-93.
Not surprisingly, Boston’s accident rate is above average, and delays are routine. Furthermore, growth projections show a 35 percent increase in vehicle traffic by 2004. Most of I-93’s downtown section (called the Fitzgerald Expressway) is elevated to preserve downtown space and minimize through-traffic. However, the highway actually divides the downtown area by restricting through-traffic connecting the central downtown district to the harbor area and eastern residential neighborhoods.
A really big dig The CA/T Project, also known as the “Big Dig” or, simply, “The Project,” is now in its eighth construction season. Regarded as one of the world’s largest public works projects, it is notable for its size and construction techniques.
The project’s final costs are expected to reach $10.8 billion, 70 percent of which will come from the federal government. Non-federal funds for the project come from state bonds and toll income generated by the Massachusetts Turnpike Authority.
The CA/T project has required 109 separate construction contracts and the services of nearly 200 construction and related companies. Ultimately, nearly every part of the city will be affected to some degree. As part of the project: * the Massachusetts Turnpike will be extended through new tunnels beneath Fort Point Channel and Boston Harbor to allow direct access to Logan Airport; * improved interchanges at the I-90/I-93 juncture and new bypass roads will be built to minimize congestion at the interchange, and a higher-capacity bridge system will connect Boston and Charlestown over the Charles River; and * ramps and a bridge will be built to connect I-93 and Storrow Drive, the principal roadway along the Charles River.
(During construction, a substantial network of temporary roadways and bypasses was established at the existing I-93/I-90 juncture to maintain traffic flow. The temporary roads will be removed when traffic is permanently routed to the new systems.)
The massive size of the project is difficult to grasp. In its most active period, it involved about 4,000 workers and 150 cranes. When it is over, dirt excavations will have totaled 13 million cubic yards – 541,000 truckloads and 4,400 barge loads – and 3.8 million yards of concrete will have been poured. The project costs about $3 million per day.
Tunneling along The first major part of the CA/T Project to be finished is the 1.6-mile-long Ted Williams Tunnel, which runs 90 feet under Boston Harbor. Bypassing the downtown Central Artery, it will provide a direct route to the airport from the Turnpike.
Essentially completed in late 1995 for less than its $1.3 billion budget, construction of the tunnel involved submersion of two 325-foot-long steel tubes. Each is capable of handling two lanes of traffic. The tunnel’s airflow requirements are so extensive that the ventilation system is housed in two buildings.
Construction of another tunnel, featuring what the project’s web site (www.bigdig.com) calls “the most extensive use of concrete-immersed tube tunnels in the United States,” is slated for the Fort Point Channel. That tunnel represents the first and largest installation of jacked vehicle tunnels in North America, and the second use of soil mix construction on the East Coast, according to the site.
The elevated portion of I-93 also is being replaced by a tunnel. And, although not all of the I-93 reconstruction is underground, that new tunnel currently is garnering the most public attention. About half the widened expressway, 160 lane miles in a 7.5-mile-long corridor, will operate within the tunnel that is being built immediately beneath the existing elevated thruway.
During tunnel construction, the entire elevated highway remains open to daily traffic. When construction is complete, the elevated highway will be dismantled and its steel salvaged.
According to Terry Brown, the project’s director of media relations, slurry wall technology has played a key role in the tunnel’s construction. It provides temporary support for the elevated highway structure and is used in construction of retaining walls for the deep excavations.
When they are finished, the tunnels will require the world’s largest ventilation system and will feature the world’s most advanced traffic management and emergency response systems, Brown says. The tunnel control system will be staffed to process data collected by more than 400 traffic monitoring cameras and other surveillance units, 292 in-road sensors and more than 3,400 air quality detectors. Other systems will monitor temperature, water drainage, vehicle height and weight, and traffic flow. They also will provide drivers with constant traffic information via variable message signs.
Bridging the Charles Construction of the three tunnels is the largest part of the CA/T project, but its most visible aspect is the Charles River Bridge, which involves construction of two bridge structures. Bridge construction now is under way following lengthy delays, which were, in part, the result of public concern over the bridge’s complicated design and complaints that it might actually worsen traffic. (One alternative, a tunnel instead of a bridge, was ruled out because it added two years of constructiontime and an estimated $100 million in costs.)
Arguments from citizens’ groups resulted in a complete redesign of the initial 16-lane, three-bridge system. Two subsequent lawsuits, dismissed in federal court, put construction behind schedule.
The bridge now under construction is described as the widest cable-stayed bridge in the world; the first to use an asymmetrical design; and the first hybrid design using both steel (in the main span) and concrete (in the back spans). To handle the huge project, the CA/T construction management team of San Francisco-based Bechtel and New York-based Parsons Brinckerhoff Quade & Douglas oversees a small army of contractors, subcontractors and related service activities.
The team, which reports to the Massachusetts Turnpike Authority, has faced a number of challenges, not the least of which were keeping the downtown area open and thriving, and maintaining the livability of nearby residential areas during nearly 14 years of disruptive construction. Peter Zuk, project director from 1991 to 1998, used to say that minimizing disruption during the project could be compared “to performing open heart surgery on someone who continues to go to work and play tennis.”
“We have done our best to keep interruptions in the downtown area at a minimum while remaining highly cost-conscious,” says Jim Gillooly, Boston’s deputy commissioner of transportation. “Performing this massive amount of construction while maintaining a vibrant commercial and residential environment has required us to be innovative in dealing with all of the apprehensions about the demise of downtown activities.”
“Although the future benefits were obvious and could not be achieved without this project, many city managers and downtown businesses feared that permanent economic damage would be one of the [project’s] end products,” says Robert Albee, past president of the Kansas City, Mo.-based American Public Works Association, and Boston’s chief engineer when the project’s initial plans and cost estimates were developed. “This is a 24-hour city, and it was mandatory that we keep it alive and thriving. A considerable number of Bostonians were convinced that the disruptions would practically guarantee irreversible damage to Boston’s very essence. Without a doubt, mitigation has been one of the most important aspects of this project.”
Now retired after 13 years on the project as director of construction services, Albee is managing director of transportation engineering for Watertown, Mass.-based VHB, a construction engineering firm. “The mitigation issue deals with keeping the downtown businesses fully operational throughout the project and maintaining high standards of livability in the residential neighborhoods,” he says. “My best estimate is that mitigation-related issues represent about one-third of the total project cost.
“That’s more than $3 billion for signage, traffic rerouting, temporary roads, clean up, noise abatement and the like,” Albee continues. “For example, we relocated $850 million worth of underground utilities in the oldest part of downtown Boston so carefully that we experienced minimal interruption in business activity. A big expense, for sure, but we obligated ourselves to this service.”
The community, in turn, has helped project management. “Boston’s business community understands the unprecedented opportunities provided by the CA/T Project, including reconnecting Boston’s downtown to its waterfront, creating 27 acres of new air rights, building an improved roadway and transportation system, and creating a cleaner air environment,” says Richard Dimino, president of the Artery Business Committee. (The committee, formed in 1988 to monitor the project’s impact on the local business community, represents more than 60 companies that employ more than 100,000 workers.)
“However, fully realizing these opportunities requires the participation of the business community, along with other constituencies in the planning, design and construction of the project in close partnership with the city, state and project team,” he says.
Good news/bad news Despite its projected benefits, the enormous costs associated with the CA/T Project have attracted a multitude of critics. The result is a flurry of allegations about runaway costs, political shenanigans, lack of adequate federal management and cost control, questionable right-of-way purchases, unnecessary delays, poor planning and disregard for environmental issues.
Reams have been written about the multi-billion dollar project. The Boston Globe and The Boston Herald, as well as The Washington Post and “60 Minutes,” have taken their shots. Additionally, in a report entitled “No Light at the End of This Tunnel,” the Project on Government Oversight, a non-partisan, nonprofit federal government watchdog, predicted that the final cost of the project would quadruple initial estimates and that construction would be completed six years late.
Not surprisingly, Brown defends the project. “The growth of the project’s cost is a function of two things – inflation and scope increases,” he says. The difference between the original rough estimate of $2.6 billion in 1982 and the $10.8 billion estimate for 2004 is equally divided between inflation over 22 years and more than 100 scope additions that reflect the process of gaining community and environmental approval.
“The $2.6 billion number didn’t include mitigation, which now amounts to a third of the budget,” Brown says. “Our budget has stayed essentially steady since 1993, when it was $7.9 billion plus inflation. The $10.8 billion includes inflation through 2004.”
The sheer ambitiousness and immensity of the Central Artery/Third Harbor Tunnel Project guarantees critics. In the end, however, if it works as expected, it will relieve one of the country’s most notorious traffic situations and will establish new watermarks for the construction industry. That will go far toward silencing the critics.
And, while Boston will feel the project’s immediate effects, they will extend far beyond the city. As Albee says, “The future of New England commerce and that of the immediate Boston area is what the Central Artery Project is really about.”
David Beck is a freelance writer in Middletown, Ohio.
Three years ago, sidewalk cleaning in downtown Richmond, Va., was mostly done the old-fashioned way – with a dustpan and a broom. City personnel pushed carts down city sidewalks while picking up litter piece by piece, street by street.
While those efforts made a difference in the city’s appearance, they were not sufficient to keep up with the cleaning demands of the downtown area. So, downtown merchants pushed for improved cleaning to help in their efforts to revitalize the area’s economy. After months of research, the Department of Public Works, with support from the Richmond Clean City Commission, concluded that a cleaner city was a safer city. And a safer city meant that people would spend more time shopping and doing business downtown. Consequently, the city began looking for something to enhance its litter collection.
In order to call attention to the city’s downtown cleaning efforts, Richmond developed distinct personalities for two mechanical sidewalk scrubbers, manufactured by Minneapolis-based Tennant. A local artist painted animated features on the machines, dubbed Bubbles and Bristles. Bubbles features light blue and white bubbles, while Bristles sports a mustache. The pair cleans the downtown sidewalks, scrubbing away oil, gas, food, beverages and animal droppings.
Richmond’s downtown is experiencing a healthy economy, and city officials believe the scrubbing equipment, along with traditional crime-fighting efforts, have helped improve the area’s patronage. More young professionals are moving into the area, more new apartments are becoming available, and new businesses are springing up.
On April 1, downtown sidewalk cleaning responsibilities were transferred to the Clean and Safe initiative of Richmond Renaissance, a local organization made up of downtown merchants dedicated to keeping Richmond’s economy strong. The program, the first of its kind in the state, now handles Bubbles. Bristles re-mains with the Department of Public Works for assignments outside Richmond’s central business district.
This article was written by Frederick Hughes, deputy director of public works for Richmond, Va.
In California, people are now driving to work on the same stuff in which they drink their morning coffee. That is because, to combat roadway deterioration caused by environmental factors and heavy traffic, the California Department of Transportation (Caltrans) increasingly is turning to alternative materials like Styrofoam, polyethylene pipe and lightweight fill to build new roads.
Working with Concord, Calif.-based Harris & Associates, Caltrans is pioneering those new building techniques to quickly reopen vital connectors, especially in the state’s remote, mountainous areas where highways are particularly vulnerable to landslides and flooding. “When the world starts to melt, roads crumble in many places, and there is little we can do to prevent it,” says Caltrans spokesperson George Otterbeck.
Last winter, the department faced the task of repairing State Highway 253, a Northern California link between Ukiah and Boonville. Heavy rains had washed out a 600-foot section of the highway, and Caltrans determined that conventional construction would have closed the road for at least three weeks. However, daily use of the road by school buses and commuters required a creative solution. Caltrans found that solution in the form of Styrofoam blocks.
“We closed the road, excavated down to about 30 feet, then constructed a fill out of 4-foot by 8-foot, 30-inch-high Styrofoam blocks,” Otterbeck says. “They weigh only 230 pounds apiece, so two people can handle them. Within 36 hours, working around the clock, traffic could be routed back onto the road. The blocks are locked together and should last for years.”
According to Otterbeck, the blocks exert less pressure per square foot than traditional materials. For example, large vehicles may exert 30,000 to 50,000 pounds of pressure per square foot on regular earth materials. But Styrofoam creates buoyancy and exerts only a half-pound of pressure per square foot on the earth. Initial costs are higher than with traditional materials ($100 vs. $60-$80 per cubic yard), but deterioration and settlement is much slower, and installation is faster.
In Mendocino County, high-density polyethylene pipe (HDPE) was the material of choice when Caltrans had to rebuild another section of SR 253. On that job, conventional 24-inch diameter HDPE culverts were capped on both ends, lowered into the excavated hold, and bound together. A lightweight aggregate was slurried around them.
HDPE is not as light as Styrofoam (25 pounds vs. a half-pound of pressure per square foot), but it is less labor intensive. Conventional construction on the Mendocino County section would have required two to six weeks of work, but the HDPE was installed in 36 hours of around-the-clock work.
In Oakland, Caltrans employed a lightweight fill material of expanded shale to reconstruct part of the I-880/Hegenberger Road interchange, which provides access to the Oakland Metropolitan International Airport, Airport Business Park and the Oakland-Alameda County Coliseum sports complex. The fill consists of hot-air extruded particles, 70 to 80 of which are semi-angular and the rest somewhat marble-shaped.
Typical roadway aggregates may weigh 150 pounds per cubic foot. Expanded shale weighs only 70 to 90 pounds per cubic foot.
One of the first traffic-calming programs in the Northeast is under way in Cambridge, Mass., with construction proceeding on three projects and three others in the planning stage. The goal of the program is to regulate traffic operations on city roadways by altering the design of neighborhood streets.
Traffic calming typically involves the strategic deployment of common streetscape elements such as curbs, sidewalks and landscaping in a way that encourages dr ivers to adhere to speeds appropriate for a residential neighborhood. Cambridge, a densely populated city of nearly 100,000, launched its city-wide program in 1997. The city features narrow streets, tight on-street parking and an increasing volume of traffic cutting through city roadways.
“We believed that the traffic-calming program would further several city-wide goals,” says Cara Seiderman, transportation program manager for the Cambridge Community Development Department. “It would improve the quality of life in the community, promote walking and bicycling, and increase public safety on our streets.”
At first count, city officials and neighborhood groups identified close to 30 locations as potential candidates for traffic calming. The most common sites were close to schools and playgrounds where children were often exposed to high-speed traffic and cut-through traffic across once-quiet residential streets.
Cambridge’s traffic-calming project began with a neighborhood meeting during which the nature of existing problems was established. Generally, both location-specific and corridor-wide issues need to be addressed regarding each street. Concepts are developed, and community feedback is solicited with respect to considerations such as the exact placement of devices, the impact of the project on parking, and the possibilities of landscaping.
Members of the city’s Traffic Calming Working Group – which includes representatives from the community development, public works and traffic departments – met with the Boston office of New York-based TAMS Consultants to plan, design and schedule individual projects.
The three projects under construction presented a variety of design challenges. * Oxford Street, located in the center of Cambridge, is exceedingly narrow, with two-way traffic and parking on both sides of the street. Since further constriction of the roadway was impractical and on-street parking could not be sacrificed, improvements focused on providing curb extensions at each intersection to visually narrow the roadway, shorten pedestrian crossing distances and improve pedestrian sightlines. * Columbia and Third streets, which allow parking on one side only, will be given curb extensions. In addition, the parking lane will be switched from side to side at various intervals to eliminate long straight-aways that encouraged speeding. * Fayerweather Street is a wide, one-way residential road that offers the city the opportunity to provide marked bicycle lanes and large landscaped areas. Huron Avenue, which traverses a small neighborhood commercial area, will be equipped with median slow-points offering pedestrian refuge, vehicular diversion and opportunities for streetscape designs.
The streets in all of the projects will be provided with elevated crosswalks at critical locations. For example, on Oxford Street, which splits a portion of the Harvard University campus, a raised crosswalk will be installed. And, on the same street, a raised intersection will be constructed at the corner of an elementary school to allow children to cross safely. Other streets will have similar devices in proximity to parks, playgrounds and housing developments.
Four previously “calmed” streets, which were designed as prototypes by city staff prior to the current program, have provided valuable lessons on the width and angle of chicanes and other horizontal diverters; the most effective vertical profile for raised intersections and crosswalks; and the relative visibility to be gained from various striping patterns and landscaping effects. Before-and-after speed surveys on the prototype streets indicate that the desired results are being achieved, with speed reductions of up to 10 miles an hour in some instances.
“The program to date can be considered a success,” says Cambridge Mayor Frank Duehay. “In addition, residents are pleased with the landscaping and visual improvements. I have no doubt that, when the program is complete, Cambridge will be a better and safer place in which to live.”
When it was built in 1939, Norfolk, Va.’s 26th Street Bridge was expected to serve the city’s trolley cars. Over time, trolleys fell out of use, and the bridge was re-fitted to serve cars, buses and tractor trailers. Still, the passage of time took its toll, and it became clear that the bridge – the only arch-shaped structure of its kind in the city – required major repairs.
Norfolk retained Vienna, Va.-based Desman Associates to handle the project. The company assessed the amount of deterioration using watercraft to access the bridge’s underside, divers to check pile conditions below the waterline and specialized equipment to perform a thermographic survey of the concrete bridge deck.
Concrete cores were removed from the deck slab and tested for strength, chloride content and overall quality. Laboratory and field test results indicated that the bridge could not carry modern specified highway loadings.
Norfolk’s Department of Public Works chose to rehabilitate the bridge and preserve its original appearance. Construction would include: * replacement of pile jackets; * reconstruction of piles; * continuous partial depth repair of the existing deck slab; * installation of a new concrete wearing surface integral with the repaired concrete deck slab; * installation of new expansion joints and streetlights; * replacement of concrete edge beams, sidewalks, curbs and gutters; and * restoration of existing bridge rails.
More importantly, because the bridge serves as a major east-west link in the city, traffic and utilities would have to be maintained during construction.
Construction progressed in three phases. Phase I involved rehabilitation of the bridge’s center section, phase II its south side and phase III its north side. Motorists had access to the bridge most of the time. (Concrete pours necessitated 11 three-day closures. Press releases were routed throughout the city before closures.)
During construction, a number of steps were taken to preserve nearby wetlands and prevent erosion. Temporary timber matting was placed in all wetlands areas and in some non-vegetated wetlands within the area. The matting was removed, and the wetlands revegetated after construction.
Additionally, at each of the bridge’s four corners, fencing was installed to protect existing magnolia trees. All curb inlets near the construction were protected with erosion and sediment control techniques.
The rehabilitation project cost $2.54 million, as opposed to the $5 to $8 million it would have cost to replace the bridge. The project was finished in 14 months.
More importantly, it allowed Norfolk to preserve a part of its past. As one city publication put it, “Using state-of-the-art construction materials, rehabilitation of the historic bridge preserved for another 25 to 30 years a part of our past, a part whose appearance is not easily duplicated by modern construction techniques, and a part whose inherent value is often underestimated.”