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I-35W Bridge Collapse and Replacement
First Response and Recovery Support
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U.S. Army Corps of Engineer's employees at Lower St. Anthony Falls Lock and Dam in Minneapolis found themselves at ground zero for a large-scale disaster response effort that began Wednesday, Aug. 1, 2007, after parts of the I-35W bridge over the Mississippi River fell on their work site around 6 p.m. Debris from the eight-lane river span bridge fell on the lock's lower guide wall and adjacent Federal property. The two lock operators working at the Lower St. Anthony Falls lock wall, about 60 feet from the bridge, assisted with the immediate incident response.
Following the emergency first response, Corps' staff assisted the incident commander, the Hennepin County Sheriff, by providing a work site, equipment and people. The St. Paul District's water control and lock personnel adjusted water levels on the Upper Mississippi River at the sheriff's request to assist with search and recovery efforts. The district's maintenance and repair crew were at the lock and dam that week completing routine maintenance work with a crane barge and small work barge. This crew and heavy equipment remained in Minneapolis and assisted the sheriff with search and recovery work and provided direct support to the U.S Navy dive team that was assigned to assist with recovery operations. This work concluded on Aug. 20, 2007, when the recovery was completed and the dive team demobilized.
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Bridge Debris Removal and Navigation
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The Corps opened the Lower St. Anthony Falls Lock and Dam to limited, local commercial barge traffic in accordance with the U.S. Coast Guard navigation notice on Sept. 6, 2007. The Corps had surveyed the channel depths and the Coast Guard determined that opening the channel to limited traffic was acceptable. On Oct. 6, 2007, all vessels, including recreational vessels, were allowed access to the channel and lower lock.
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Bridge Replacement Design and Construction
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The Corps assigned a project management liaison to coordinate with the Minnesota Department of Transportation on design and construction issues related to Corps real estate, permit requirements and operational impacts. The Corps' only dredged material placement site within the navigation pool is under the bridge's north abutment span and will continue to be available for future use.
The Corps amended the existing real estate easement agreement that the Department of Transportation has for use of Corps' lands along the south bank. The agreement establishes conditions for use of the real estate and addresses impacts on Corps operations. The new bridge width and alignment will prevent the Corps from placing lock dewatering bulkheads from a barge mounted crane. Under the new agreement terms, the Department of Transportation will investigate design and construction of access to facilitate a land-based crane operation. The construction contractor will need to replace the Corps' south approach access road that was removed to facilitate construction.
During the 2008 navigation season, the Coast Guard posted surface water restricted zones in the immediate vicinity of the bridge, but these did not impede normal river traffic. The navigation channel and lock were closed for short periods of time in June and July to facilitate safe placement of large precast sections of the main bridge span. The bridge opened to traffic in September 2008.
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