Photo shows a rescue basket lowered from a helicopter.
The break sent several feet of water rushing on to River Road.
Rescuers used helicopters, boats and fire trucks rescued more than one dozen people trapped in vehicles after the 66-inch water main burst.
Terrified drivers and passengers remained in their vehicles, waiting to be rescued as water four feet deep gushed around them.
In one rescue, a firefighter in a small boat helped two women out of a stranded SUV, the windows of which had frozen, reported WTOP's Neal Augenstein who was about 30 feet from the scene. The boat was then sent to the side of the road where rescuers pulled them to safety.