[caltitan]

I've seen many underground storage tanks in my line of work and they do have some dirt and particles that have settled on the bottom of the tank. I've never heard any tank installation/removal contractor discuss whether a fuel drop (tank refill) actually causes enough turbulence to suspend those particles enough where they suddenly are pumped out and into the product lines heading toward an active dispenser. But knowing what I know about how these tanks work I think it could be possible. However, it would depend on the type and age of the fuel delivery system and quality of gasoline that the station uses. California has some of the toughest tank construction and operation regulations so it is very difficult for sediment or debris to enter the tanks now then in past years.