In 10 days, we will observe the first anniversary of the collapse of the I-35W Mississippi River Bridge in Minneapolis, Minn., at a toll of 13 dead, more than 100 injured and the reputation of a state shattered.

Within hours of the previous bridge's demise, officials were pledging to rebuild the bridge at an accelerated pace, not only to put the horrors of the old bridge in the past as fast as possible, but also for practical reasons. The state pushed an aggressive timetable to replace the steel bridge, which was a critical link to northern Minneapolis and its suburbs when it collapsed on Aug. 1, 2007.

The I-35W bridge carried more than 140,000 vehicles a day, and the loss of the bridge has been costing $400,000 per day in lost revenue, increased commuter expenses and burden on surrounding roads, according to Minnesota's DOT Web site. The collapse of the bridge affected not only road transportation, but also river, rail and air transit.

In the few days that followed the collapse, the Minnesota Department of Transportation (DOT) was planning a replacement bridge, later named the St. Anthony Falls (35W) Bridge.

Where the I-35W bridge once stood, a new $234 million bridge is nearing completion. Early this month, the bridge was 80 percent complete. Though it will not be open by the anniversary of the tragic collapse of its predecessor, it is on track to open to traffic as early as September — three months ahead of schedule.

The St. Anthony Falls Bridge's "soaring yet simple" design was made public in October by the state's DOT and the companies it hired to build the replacement bridge.

In the previous bridge's place, the new bridge will actually be two concrete bridges that span the river, one for northbound traffic and one for southbound. There will be an 8 foot 8 inch space between them.

"Each side will have five lanes, for a total of 10 lanes of traffic. The combined bridge width will be 189 feet," the state's DOT Web site explains. "The previous bridge had 8 lanes of traffic and was about 80 feet narrower.

Federal investigators have cited a design flaw in some of the earlier bridge's gusset plates.

"The new bridge has a different design than the old bridge, which was 'fracture critical' — meaning when one part failed, the whole bridge fell," the Associated Press reports. The new St. Anthony Falls' Bridge, on the other hand, is a "redundant structure," with many different levels of tension holding the bridge together. "If one gives out, it gives us time to fix the problem," Kevin Gutknecht, a spokesman for the Minnesota DOT, said.

Structural enhancements include the use of high-performance concrete to provide superior durability and multiple levels of structural redundancy to provide a long-lasting bridge for the future that will be economical to maintain.

Crews working on the new bridge poured 7 ft. of concrete on the main river span and continued painting the south side last week. According to the project's DOT page, 48,700 cubic yards of ready-mix concrete will be used to build the new bridge with approximately 15,800,000 lbs. of steel reinforcing bars

Also protecting the new bridge will be a state-of-the-art sensor and monitoring system built into the bridge that will allow for easier and more comprehensive monitoring throughout the bridge's lifetime.

Flatiron Constructors, Inc. and Manson Construction Co., in a joint venture, are the main contractors on the new bridge. The contract requires completion by Christmas Eve 2008. But by finishing sooner, which the firms appear to be on track to do by a stretch, the builders can earn multimillion-dollar bonuses.

Bill Halsband, vice president at accelerated-construction firm Mammoet USA, recently told AP that he is not aware of any previous bridge of this size that's gone up so fast using conventional construction methods.

Despite the hurry-up schedule, Gutknecht recently told AP that there is no reason to think the rapid pace will compromise safety. Several layers of quality control include outside inspection of the plans, and of each stage of the work before it happens, he continued. The state's DOT also has a team of inspectors on site, constantly reviewing every facet of the job.

In addition to a design flaw in some of the bridge's gusset plates, federal investigators also have said that the heavy loads of construction materials that had been placed on the bridge over the most vulnerable gussets probably contributed to the collapse. A final National Transportation Safety Board report on why last year's collapse occurred is expected in the fall.

As of last week, the remains of the collapsed I-35W bridge remained where they've been for nearly a year.

Earlier:

Two Tales of Terror/Tragedy

Design Error in Fatal Minneapolis Bridge Collapse

The 12 Big Stories of 2007

Resources

I-35W St. Anthony Falls Bridge
Minnesota Department of Transportation

Design for New Minnesota Bridge Unveiled
by Brian Bakst
The Associated Press, Oct. 8, 2007

Minneapolis I-35W Bridge on Track to Open Early
by Patrick Condon
The Associated Press, June 20, 2008

Answering Your New I-35W Bridge Questions
by Darcy Pohland
WCCO.com (CBS), July 14, 2008