Four people are dead, 79 injured and 20 missing after an Interstate 35W bridge going over the Mississippi River collapsed in Minneapolis yesterday during rush hour, reported the Minneapolis Star Tribune. In Iowa, state officials are waiting for investigators to determine what caused the collapse to determine whether changes need to be made to its 25,000-bridge system.

According to DOT spokeswoman Dena Gray-Fisher, the primary precaution in place is to inspect every bridge every two years. If a deficiency is found, a correction is made or a restriction placed on the bridge that limits weight, speed or type of vehicle.

“With inspection, we’re feeling very confident in Iowa about the safety of our bridges, because we do have due diligence in inspection,” Gray-Fisher said. “If any issue is discovered during inspection, we take immediate corrective actions and monitor them more often.”

Because of funding shortages, the Iowa DOT has been slower to replace some of the bridges with restrictions on them, Gray-Fisher said. Many of the bridges being replaced now were constructed in the 1960s and contractors are using much better concrete, steel and designs.

Iowa State University’s Bridge Engineering Center was involved with researching a fiber optic monitoring system on the Interstate 235 reconstruction project. With a federal grant, engineers were able to install fiber optic strain gauges on the East 12th Street bridge and the pedestrian bridges at 40th and 44th streets, which tracked the bridge’s strain history, but the fiber optic system was expensive and research stopped when funding ran out, said Lowell Greimann, who recently retired as chair of the civic, construction and environmental engineering department at ISU but still does research for the bridge engineering center. The East 12th Street bridge also has a high-performance steel that is designed to be stronger and more durable.

Both of these features, Greimann said, are in development stages across the nation. “Most likely what happened yesterday will bring this all up again and of course there could be a push to start more continuously monitoring bridges electronically, so maybe we can get a warning on some of this stuff,” he said. “But there’s a ways to go before that technology is available and affordable.”