Concrete crashed onto a Washington, D.C., train station platform during the evening rush hour Nov. 17, but no one was injured. Investigators are checking why the chunks of concrete fell from the ceiling of the Farragut North Metro station in downtown Washington, D.C., an underground Metrorail station. The largest chunk was the “size of a human head,” says a Washington, D.C,. fire department spokesperson. The concrete fell approximately 25 ft to the platform, creating a debris field that was 20 ft across, he said. No one was injured. Investigators are homing in on the possibility that construction crews doing roadwork
Arch dams, classically curved monoliths situated in narrow valleys, are not as common as other types of dams, such as embankment dams and gravity dams. ENR takes a look at some of the biggest arch dams in the world, both completed and under construction.