People, cars and a train weren't the only things that the I-35W bridge took out on its six-story plummet into the Mississippi River. Part of it also landed on a lock and dam operated by the U.S. Army Corps of Engineers.
"The collapse fell on the guidewall," says Aaron Snyder, spokesman for the Corps St. Paul District. Though crews have not yet been able to pull the mangled bridge from the lock to assess the damage, another district official says it "appears very slight."
Tudor Van Hampton
Portion of I-35 bridge damaged Lower St. Anthony Falls Lock and Dam. Two other lock and dams, one upstream and one downstream, are closed to commercial traffic while recovery operations proceed.
The lock, located just upstream from the collapse, is being used to move recovery boats back and forth from the scene. Two other locks, one upstream and one downstream, are shut down to commercial traffic While recovery work continues.
Local police are still treating the site as a crime scene, though state and federal officials have not indicated that foul play caused the collapse. The National Transportation Safety Board is leading a federal investigation. State officials are leading independent but coordinated investigations.
Recovery efforts are moving forward nearly two days after the collapse of the I-35W arch deck truss Bridge in Mineapolis. State officials have confirmed that five people are dead and at least eight are still missing in the wreckage.
Sonar equipment has identified several "targets" in the river, including vehicles and parts of the fallen bridge, state and local officials say, but divers have had a difficult time maneuvering around debris due to murky water and unpredictable currents.
The response operation has now shifted fully from rescue to recovery. "We don't believe there are people who are alive," says Minneapolis Mayor R.T. Ryback.
Tudor Van Hampton
Aaron Snyder, Army Corps of Engineers spokesman, says draw-down of river level caused turbulence that hampered recovery operations.
On the day after the collapse, the Corps coordinated the flow of the three locks and dams around the site to "draw down" the level of the river to facilitate easier diving and recovery. It also has moved in a light crane and "handy flat" barge to aid in recovery of vehicles and bodies.
The initial draw-down created suction that forced divers to slow down the recovery effort. "There was some turbulence in the debris field," Snyder says. "It's a tight spot and hard to get to."
The "pool" around the wreckage typically is between 4 and 14 ft deep. It now is about 2 to 3 ft lower. Overall, flow through the area has been cut to 1,350 cu ft per second, about 15% of normal capacity.
"It's a very good thing we are in a drought," adds Snyder.
With barge traffic shut down, some businesses and pleasure craft are affected by the collapse.
But already-light traffic through that part of the Upper Mississippi makes the collapse "less of an impact had it been downriver," says Ann Calvert, principal project coordinator with the Minneapolis development and community planning dept.
Aggregates Industries Inc., which supplies construction materials, and American Iron, a recycler, are the major businesses affected by the waterway shutdown, says Calvert.
Average tonnage through the Upper and Lower St. Anthony Falls, just upstream of the collapse, is 1.8 million tons, according to the Corps. Total tonnage last year was 1.3 million tons.