The Lacey V. Murrow Memorial Bridge across Lake Washington opened in 1940. More than a mile long and at the time the longest floating concrete bridge in the world. Lake Washington was too deep for traditional piers so engineers built the bridge on massive hollow concrete pontoons anchored to the lakebed. For fifty years it carried traffic between Seattle and Mercer Island, later becoming part of Interstate 90. In November 1990 the bridge was undergoing renovation. Workers had removed watertight

The Delaware Memorial Bridge That Almost Didn't Open engineering history, infrastructure, bridge