It was rush hour on a Wednesday -- just after 6 p.m. on Aug. 1, 2007 -- on the Interstate 35W bridge over the Mississippi River near the University of Minnesota. The bridge, which handled 140,000 vehicles per day, was scheduled for some repair work, so heavy construction equipment and materials were loaded onto the bridge.
Suddenly, the bridge gave way with the central span falling into the river. Cars and trucks, concrete and steel, plunged into the waters of the Mississippi.
According to the National Transportation Safety Board accident report, the bridge “experienced a catastrophic failure in the main span of the deck truss. As a result, 1,000 feet of the deck truss collapsed, with about 456 feet of the main span falling 108 feet into the 15-foot deep river. A total of 111 vehicles were on the portion of the bridge that collapsed. Of these, 17 were recovered from the water. As a result of the bridge collapse, 13 people died, and 145 people were injured.”
The I-35W bridge supported eight lanes of traffic, four in each direction. Two lanes on each side were closed in preparation of moving on the construction materials and equipment for a scheduled concrete pour at 7 p.m. The materials were in place by 2:30 p.m., and when the bridge collapsed, 25 of the vehicles that fell were either construction vehicles or vehicles owned by construction workers.
A caller on 911 notified the Minnesota State Patrol about the bridge collapse at 6:05 p.m., and dispatchers sent out calls to Minneapolis fire and police departments. At 6:08, Minneapolis 911 made a distress call requesting all available emergency responders.
“The Minneapolis police captain responsible for the on-scene investigation estimated that 100 citizens assisted in the total rescue effort,” the NTSB reported. “These people included construction workers who had just left or arrived for shift change, passersby, a group of medical personnel who were in training at the nearby Red Cross building, and a number of University of Minnesota students and staff. He said that 30-40 of these individuals went into the river to pull drivers and construction workers to safety.”
Ambulances, fire engines, and other public safety vehicles arrived, and by 6:25, the sheriff’s office had established a river incident command site near the University of Minnesota River Flats area. Within the hour, 12 other agencies responded with 28 watercraft to participate in the river rescue operations. This remained active until 7:27 when the commander changed the water operations from rescue to recovery, according to the NTSB accident report.
In the hours and days that followed, officials confirmed that 190 people were on or near the bridge at the moment of the disaster. Of those, 13 were killed, 34 received serious injuries, 111 received minor injuries, and 32 were not injured or were unknown. Medical records show that 145 people were transported to 12 area hospitals, medical centers, and clinics.
With one of the major bridges in Minneapolis down, fast action was needed to replace the bridge. Within three days, Congress had authorized $250 million for replacement funds, and the Minnesota Legislature set up a Joint Committee to Investigate the Bridge Collapse.
This Joint Committee, in their report, noted, “When a bridge collapses, so does public faith in government. It is therefore essential that the role of government in maintaining and replacing our infrastructure be subject to the most rigorous and objective scrutiny, not to ascribe blame but to proscribe future disasters.”
The Joint Committee investigation went on for several months and ended up with recommendations that the Minnesota Department of Transportation, as well as the Minnesota Legislature, could make to improve their policies in relation to bridges.
The National Transportation Safety Board conducted an examination, not of policies, but of the wreckage of the bridge, and determined that “the probable cause of the collapse of the I-35W bridge in Minneapolis was the inadequate load capacity, due to a design error by Sverdrup & Parcel and Associates Inc. of the gusset plates at the U10 nodes, which failed under a combination of (1) substantial increases in the weight of the bridge, which resulted from previous bridge modifications, and (2) the traffic and concentrated construction loads on the bridge on the day of the collapse.”
The gusset plates held major beams of the bridge together, and the investigation revealed they were half as thick as they should have been. Sverdrup & Parcel and Associates of St. Louis designed the bridge in the early 1960s and work began on some of the piers in 1964. Hurcon Inc. built the bridge, and it had opened to traffic in 1967. It was inspected every two years by the Minnesota Department of Transportation until 1993, then annually after that.
Following the incident, concern for other bridges was high, both among officials and the public. Funding to increase inspections and infrastructure improvements became a prominent issue, and led to many discussions including one in the 2008 state Legislature regarding a proposal to raise the gas tax. The bill passed both houses, but then-Gov. Tim Pawlenty vetoed it, and the Legislature passed an override of the veto. It had become a difficult topic, but the issue of bridge and infrastructure safety and funding had grown into an important part of public discourse.
On Sept. 19, 2007, MnDOT announced that Flatiron Constructors and Manson Construction Co. would rebuild the bridge for $234 million. The new bridge was built, and it was opened to traffic on Sept. 18, 2008.
During the year that the bridge was down, a major transportation route in the Twin Cities was missing, and thousands of people had to restructure their daily routines. Each time they took a detour, they were reminded of the tragedy and of the disruption in their lives.
“Bridges are about not having to deal with rivers,” wrote John O. Anfinson in “The City, The River, The Bridge.” “By crossing over a river on a bridge, people do not have to think about how far down it is, how steep the banks are, how fast the water is flowing, or how deep it is. They do not have to consider how clean or dirty it might be, or whether it is fit for aquatic or human life. The Great River entered a person’s life for only seconds when crossing the old I-35W bridge, if they were aware of it at all. Only when the bridge fell into the river did these aspects become relevant.”