The Environmental Protection Agency says millions of acres of these sites are now being used for other purposes — such as homes, shops, offices, and parks.

While the DOD is working to assess these areas, and prioritize them for cleanup, often it's civilians who are first to come into contact with unexploded ordnance, and it's the military's responsibility to take care of it, cradle to grave.

In 2017, the EOD team at Travis Air Force base responded to more calls for assistance with military munitions from local law enforcement than any other unit in the Air Force.

The team gets calls from local law enforcement a couple times a week, even if it's just for some information on something they think they might have.

Left-over munitions on defunct military bases aren't the only calls Travis EOD receives. Many runs deal with old explosives from conflicts like the world wars, where soldiers would bring home unexploded ordnance as souvenirs.