The Federal Highway Administration will give an environmental award to Iowa for its work in building a bridge across a tree-filled river without tearing up the valley. Federal Highway administrator Mary Peters explains the job’s part of the Highway 20 project slated to be finished next year.She says construction methods that stay within the “footprint” of the bridge are minimizing the effect of the work on the old-growth forest and the wetlands around the river. Peters admits the techniques used to avoid trampling the forest and wetland added fifteen to 20-percent to the cost of the bridge. That money could have gone for more concrete, she says, but it’s also important to invest in preserving the environment. Bobby Blackman is a division administrator for Iowa and says this is the first time these innovative construction techniques have been used. A typical construction would use cranes down on the ground lifting steel into place, but because this area’s environmentally sensitive, he says the steel was all “jacked into place” from one end of the bridge. Engineer Blackman says it begins with the abutments that will hold up the bridge, and the first of many steel spans that will make up the bridge. Then an additional span of steel was added to the first and pushed on to the next abutment, a process that was repeated till the span reached all the way across the valley. Though the technique costs more, Blackman says it does not add any risk for workers building the bridge.She says it is probably less dangerous, he says, than the typical procedure that has cranes all along the bridge’s path lifting heavy beams up into the air. The bridge and that stretch completing highway 20 won’t be done till 2003.
