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.

WASHINGTON — Officials say the Potomac River is safe to navigate once again after a plane and helicopter collided mid-air near Ronald Reagan Washington National Airport (DCA) and crashed into ...

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 ...