Tarp shelters Interstate-35W bridge reconstruction

On a hot August day in 2007, rush-hour commuters on the Interstate-35W bridge in Minneapolis, Minn., felt the concrete and metal beneath them give way in one of the nation’s worst infrastructure collapses. Thirteen people died, approximately 100 people were injured, investigations began and, within months, a new span took shape over the Mississippi River. Flatiron Construction Co., Longmont, Colo., and Manson Construction Co., Seattle, Wash., formed a joint venture to build a 1,216-foot, 10-lane replacement bridge in a record-breaking 427 days.

This meant working around the clock, including the raw winter months for which the Twin Cities are famous. Flatiron and Manson called on Canamer® International Inc., Winona, Minn., for help in taming high winds and below-zero temperatures. Canamer fabricated a supersized tarp from Polycan® 12-350 24-mil high-UV woven poly in four sections for assembly on three-story structures in the concrete casting yard. Tarps were reinforced with seatbelt webbing, fitted with brass grommets and heat welded at the corners. The 2,200-pound tarp protected workers from the harsh winds and allowed poured concrete to cure evenly to guarantee its strength and longevity.

Before its collapse, the I-35W bridge carried 140,000 vehicles a day. The new bridge has two additional lanes, sensor systems that will monitor bridge vibrations and an estimated 100-year lifespan. And because the construction was weatherproofed and moved forward despite the coldest temperatures, the bridge opened on September 18, 2008.