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p11 bridgeThe Interstate 270 Mississippi River Bridge.

Photo courtesy St. Louis Regional Freightway
By DENNIS GRUBAUGH

    Fifty may be the new 40, but when it comes to heavily trafficked bridges, 50 is downright ancient.
    The Interstate 270 Mississippi River Bridge crossed the half century point this year, and supporters on both sides of the river are actively seeking to replace it.
    Two public meetings have been held to elicit opinions. The bridge is considered Illinois’ jurisdiction, even though the costs would be split 50-50 by the two states.
    “We’re seeing higher traffic volumes, and we see a need,” said Kirk Brown, Illinois Department of Transportation District 8 program development engineer. “That one is coming to an end of its useful life. We know we are going to have to replace it before too many years.”
    IDOT is just initiating a study to determine whether the bridge will be rebuilt where it’s at or relocated slightly, like the Chain of Rocks Canal Bridge was a few years ago.
    “Right now, we’re anticipating it will be a new structure. Missouri right now is conducting its own study on widening 270 from the river out to I-70, to six lanes throughout. We’re anticipating that any new improvement would likely be a new bridge with a possibly new alignment. But we have to study the environmental considerations. That helps determine where you can build and what the impacts are,” Brown said.
    The bridge is just over a mile long and extends well into Illinois.
    As part of the public process, IDOT and MoDOT have been identifying groups of advisors, people from the public, private and community sectors who can help shape what the ultimate improvement will be.
    Asked about potential price tags, Brown said a lot will depend on how long it takes to build the project and when it could be started.
    “We’ve seen $170 million as a rough estimate. We don’t anticipate it will be any kind of a marquee project like the Stan Musial Veterans Memorial Bridge,” Brown said. The Musial project was around $695 million.
    The IDOT study should take three to five years.
    “We think it’s going to be a shorter study. Essentially we know we have to connect the dots between both sides of the river so there’s not a lot of play about where the actual location will be,” Brown said.
    IDOT and its engineering consultant team, aided by input from the public, will inventory existing conditions (such as traffic data and crash history), identify and document environmental constraints, and develop and refine improvement alternatives.
    IDOT has said it is optimistic at this point to think that the bridge could be done within the next 10 years, because of the uncertainty of funding. However, officials could get it “fast-tracked” if the need is proven.
    The IDOT website offers this description of the current bridge:
    “About 51,000 vehicle trips are made each day across the bridge, with approximately 17 percent of these trips being truck traffic.
    “The structure is composed of 43 spans with a total length of over 5,400 feet.  The structure carries four lanes of traffic, two in each direction.  Over the life of the structure, numerous repairs have been made, from expansion joint replacements, pin and link replacements, repairs to the structural steel, and repairs to the substructure.
    “In addition to repairs, this structure has seen a significant increase in traffic from a projected average daily traffic of 19,800 vehicles per day in 1975, to over 51,000 vehicles per day today.  Because the structure is nearing the end of its design life, additional repairs have become necessary and roadway geometrics have become sub-standard.  This has led to the determination by IDOT that this structure be replaced.”
    The study website is: http://www.idot.illinois.gov/projects/i-270-over-the-mississippi-river