The Concrete That Holds When the River Rises

In 1993, the Great Flood swallowed towns along the Mississippi. In Quincy, Illinois, sandbag walls crumbled one after another. But the Bayview Bridge stood. Engineers later explained that its pilings had been driven sixty feet into bedrock — far deeper than anyone could see from the surface. The water raged for weeks. The bridge held. Margaret Chisholm was a nurse in Quincy that summer.…