I dont see and military vehicles hooked to the hoses. It is more like plain water from fire hydrants. If the military was going to send trucks to the scene with chemicals to wash the helos from fueling they could have just sent trucks to pick up the SF teams. They were in LA for Gods sake they werent worried about being shot while exfiltrating.
its how you rinse fuel off the choppers from midair refueling so static electricity doesnt cause a fire.
your right, Ft Bragg is in a small town.