Engineering company that investigated the 35W collapse will look into why cables failed on Sabo span.
The same company that investigated the Interstate 35W bridge collapse will examine why cables failed on the Martin Olav Sabo Bridge, whose emergency closing and disruption of traffic and trains is stretching into a fourth day.
Wiss, Janney, Elstner Associates Inc. landed a contract not to exceed $100,000 with Minneapolis and Hennepin County, which did not put the project out to bid. Instead, the Illinois-based firm was picked from a pool of on-call consultants solicited by Hennepin County every three years through requests for proposals, according to Debra Brisk, assistant county administrator for public works.
Workers on Wednesday finished installing two of four support structures needed to stabilize the bicycle/pedestrian bridge, keeping traffic off Hiawatha Avenue S. between 26th and Lake Streets. Minneapolis officials said the remaining support structures will be placed in the next day or two, after which the bridge will be sound enough for workers to try to release tension from a set of cables linked to a cracked anchor.
The bridge has been closed since Sunday, after a set of cables broke loose from the tower.
Mayor R.T. Rybak noted the inconvenience in an e-mail message Wednesday, thanking commuters for their patience.
"It is unfortunately necessary to keep the public safe while Public Works teams stabilize the bridge," he said.
City engineers are receiving aid from San Francisco-based URS Corp., the design consultant for the four-year-old bridge. URS was also a consultant on the I-35W bridge before its 2007 collapse, and it paid $52.4 million in 2010 to settle a lawsuit brought by victims who accused the company of missing warning signs of faults in the structure.
Workers at the Sabo Bridge are using computer modeling, measuring the loads on jacks on the shoring structures and determining cable tensions to evaluate the span's stability, according to Minneapolis officials. Inspectors are also looking for any new signs of cracking or other strains on the cables.
The $5.1 million Sabo Bridge was built under supervision of Hennepin County and was opened in November 2007. Ownership was transferred to Minneapolis in 2008.
Records show that the bridge's 18 sets of cables and cable anchors received the highest possible ratings from inspectors every year.
As officials work to ensure the bridge is sound, transportation delays continue. Buses will transport passengers between the 38th Street, Lake Street/Midtown and Franklin Avenue stations on the Hiawatha light rail line, although trains are running normally between Target Field and Franklin Avenue stations and between the Mall of America and 38th Street.
The detour is adding about 15 minutes to commuting times, said Metro Transit spokesman John Siqveland. "Most customers seem to be dealing with the inconvenience," he said. Transit officials suggested that some commuters could avoid the temporary delays by taking regular bus routes instead of the train.
It is unclear how long the rail line will be interrupted.
"We're just taking it day by day," Siqveland said.