I-90 Mississippi River Bridge - Potential Rehabilitation or Replacement

Potential Rehabilitation or Replacement

Although the current bridge has no weight restrictions and operates at an acceptable level of service, there are number of problems with the bridge and surrounding roadways:

• The deck is deteriorating, the most pressing issue in the short term.
• The bridge is of an obsolete, non-redundant structural design similar to that of the Hoan Bridge in Milwaukee, Wisconsin, which suffered a substantial structural failure. After the Hoan Bridge incident, the I-90 Mississippi River Bridge was hurriedly inspected and found to be in satisfactory condition, but concern about the basic steel structural design remains.
• A lack of standard shoulders inhibits emergency responses to incidents on the bridge and does not provide enough room for disabled vehicles to get out the traffic lanes.
• There are issues with the interchange on the Minnesota side, including a curve on the main travel lanes that is sharper than desirable for an interstate, a confusing design, and congestion on some of the ramps.
• There are capacity problems at the Dresbach Rest Area on the Minnesota side, which currently has only limited room for expansion. Compounding the problem, it is currently accessible from the eastbound direction, even though it is intended for westbound traffic only.
• There are no provisions for bicyclists and pedestrians on the bridge.

In 2006, Mn/DOT commissioned a study on ways to rectify some or all of these issues. Some of the options that were presented included:

• Replacing the deck only, estimated cost $23 million
• Widening and rebuilding the existing structure with either additional piers or strengthening the foundation, estimated cost $40–$58 million
• Building a new westbound girder bridge and converting the existing bridge to eastbound only, estimated cost $63 million
• Building a new girder bridge, extradosed bridge, or cable stayed bridge, and demolishing the existing one, estimated cost $59–$71 million

Selecting a preferred alternative will take further studies, but the least costly option that would address the non-redundant design of the existing bridge is $58 million, while the least costly total replacement option is $59 million. There are also a number of concepts for rebuilding the interchange on the Minnesota side, depending on whether the bridge is rebuilt or replaced. Complicating construction will be the proximity to steep bluffs and an active railway on the Minnesota side, proximity to the La Crosse Municipal Airport, which could limit the height of any towers, and barge traffic, which restricts where piers may be placed. Construction is currently planned for 2013.