This $615 million project is key to cleaning up the Potomac River. When heavy rain strikes a centuries-old neighborhood in Alexandria, Va., the city’s pipes can’t handle the volume.

investigators have completed their work at the scene where both aircraft fell into the Potomac River in the deadliest U.S. air disaster since 2001. The National Transportation Safety Board offered ...

A National Oceanic and Atmospheric Administration plane used a green laser Saturday to search the Potomac River for helicopter parts amid the investigation into the Jan. 29 collision. The NOAA ...