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| Minnesota Department of Transportation - I-35W Bridge |
| By Chris Petersen | |||
| Friday, 29 February 2008 | |||
 High priority has been given to rebuilding Minnesota’s I-35W bridge. MNDOT expects to complete it by Dec. 24.
Reconstructing the bridge obviously was a high priority for MNDOT, and it began its work last October. The project is slated for completion by Dec. 24, condensing work that would normally take up to three years to complete into barely more than one. MNDOT Project Manager John Chiglo says such a herculean task is necessary not only to restore one of the state's important access points, but also to rebuild the trust and confidence citizens have in the department and its infrastructure. The original bridge spanned 1,907 feet across the Mississippi River, and carried nearly 140,000 vehicles daily, according to MNDOT. It collapsed on Aug. 1, 2007, resulting in the deaths of 13 people and more than 100 injuries. Investigations into the exact cause of the collapse are still ongoing. Reconstruction of the bridge was fast-tracked in October, with the joint venture of Flatiron-Manson selected as the prime contractor for the project. The new bridge is a design/build project, and will be expanded from eight lanes on the original bridge to 10. The bridge is being constructed with approximately 48,700 cubic yards of pre-cast concrete. Chiglo says the project is on track to meet its goal of being completed by Christmas. “Design is approximately 75 percent complete as of today, and we've completed all of the major drill shafts for the main river bridge,” he says. “We've started the construction of the footings and we've also started the construction of the pier columns, and last week we started the construction of the pre-cast segments to be used in the construction of the main river span.” On the Fast Track “Normally, it would take two-and-a-half to three years to build [one of] these bridges,” Chiglo says. However, the I-35W project is being built in almost half that time. To meet the project's challenging deadline, Chiglo says crews are working in multiple shifts, 24 hours a day, seven days a week, including holidays. “On a normal project, they would probably have one crew drilling shafts, but on this project they had four crews drilling shafts,” Chiglo adds. “Everything is in multiples as far as constructing this bridge. That's what's allowing us to build this in the time frame we've been given.” Flatiron Project Manager Peter Sanderson says such a compressed schedule is nothing new for his company, as the contractor has worked on high-priority rebuilds before. “The company's done a number of these,” he says. “We did a number of the emergency earthquake retrofit projects in California after the Bakersfield earthquakes.” Also helping crews meet the deadline is the project's status as a design/build project, Chiglo says. A traditional approach would likely mean the bridge would still be in the design phase, he says, but design/build's overlapping of design and construction made it possible to get started right away. “What design/build allows us to do is begin construction earlier,” Chiglo says. “I don't think design/build is meant for every project, but I believe design/build was the process to be used in this project.” Dressing For the Weather The other mitigating factor in completing the project on time is the weather, which in Minnesota can mean incredibly cold winters and high winds. However, so far the project has not been affected very much by the weather, something Chiglo attributes to the preparations of the contractors. “Both Flatiron and Manson have a great deal of experience in working in cold weather conditions, so they've aggressively pursued cold weather protection for this project,” he says. For instance, the pre-cast bridge segments are being poured inside four heated shelters on the casting yard site. “It's something that our local contractors are very familiar with, but not at this scale,” Chiglo says. The preparation has paid off, he adds. “There's been very few days that they have not been able to work because of the cold weather,” Chiglo says. Rebuilding Trust Just as important as rebuilding the bridge is rebuilding the confidence of Minnesotans in their bridges, Chiglo says. “One of the challenges of this project is that we need to reestablish the public trust in what civil engineers do on a daily basis, so trying to communicate that clearly to the public is not so much of a challenge as it is an ongoing effort not only of MNDOT but also the contractor,” he says. Structurally, the new bridge is designed to last at least 100 years. “It just goes to show the quality of the materials that are being used today and the quality of the design,” Chiglo adds. Instruments are also being installed on the bridge to monitor its performance. These include temperature sensors, salt concentration meters and acoustic monitors to gauge the strength of steel tensioning strands. Such additions allow the bridge to “talk” to MNDOT and update the department on its condition, and MNDOT is also ensuring that it talks to residents about the project on a regular basis. “We conduct a weekly sidewalk superintendent talk,” Sanderson says. “We get about 100 people to come and I think that number will go up around spring.” The talks take place on a bridge overlooking the project site, and Chiglo says public response so far has been favorable. “It's new to the department,” he says. “We've had some very intensive communication elements in past projects, but not as important as this one, because of the circumstances.” On Track Even with the truncated schedule, Chiglo says the combination of intensified efforts, design/build coordination and contractor experience has resulted in a smooth project. He says motorists can expect to have their connection to the heart of Minneapolis restored by the new year. “We are very comfortable with where we are in the schedule, and very confident that we are going to have this bridge back in operation on or before Dec. 24, 2008,” he says. Noticeable Impact The I-35W collapse is having a small but clear effect on Minnesota's economy, the state says. According to a report released by MNDOT and the Minnesota Department of Employment and Economic Development, the loss of the river crossing has not only inconvenienced commuters, but also created demonstrable losses to the state's economy due to its effect on commercial traffic. “MNDOT's initial study concluded that road-user costs due to the unavailability of the river crossing would total $400,000 per day,” the report says. This figure includes the value of additional travel time caused by detours as well as additional operating costs for vehicle owners. Although commuters make up the largest portion of that figure - $247,000 worth of auto travel time - the report concludes that it would not have a major impact on the state's economy. “On the other hand, the $153,000 in longer road time for commercial truck drivers and higher operating costs for all road-users due to the bridge collapse have measurable economic impacts,” the report says. The report concludes that the average daily net economic impact is a $113,000 reduction in the state's economic output. “These impacts are concentrated in the Twin Cities and translate to about 0.01 percent of the state's economy on an annual basis.” That might not seem like much, but the report warns that local employment could be impacted. “Actual job losses will depend on how effectively road-users mitigate the economic losses and employer reaction to a possible temporary decline in sales,” the report says. |
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