18 month investigation
18 March 2008
The US National Transportation Safety Board says it may take as long as 18 months to fully investigate the causes of the August 1 bridge collapse in Minnesota, Minneapolis, US.
The Interstate 35W bridge over the Mississippi River collapsed during the rush hour on August 1, throwing more than 50 vehicles into the water. Eleven people were killed and 60 were injured.
The eight-lane bridge was one of the key routes between Minnesota's ‘Twin Cities’ of Minneapolis and St. Paul. A steel arch structure, it was built in 1967 with a main central span of 140 m. Its total length was 580 m and at its highest it was 20 m above the Mississippi.
A terrorist attack was immediately ruled-out as the cause of the collapse, indicating some sort of massive structural failure was to blame. Construction work to repair parts of the road surface and safety rails was underway at the time of the collapse, but it is unclear whether this contributed to the tragedy.
According to the state Department of Transportation, the bridge passed a major inspection last year, with no sign of structural flaws. However, two previous inspections had found it to be “structurally deficient”.
