I believe in the States, the EPA Regs are quite tight concerning Sulfur Storage. Most Refiners transport their sulfur via trucks or Railcars. Of course onsight storage is usually a traditional sulfur tank. In the case of a Sulfur Storage emergency, where the Storage tank is out of service or contaminated, I have seen Refiners modifiy their Sulfur Pit/Storage unit pumps to discharge directly to trucks and Railcars.
With that said, a Refiner has to work closely with their local regulatory agencies to come to agreement for any emergency storage. Typically, Refiners will usually have to shed Crude Rate (not a good thing) to work through storage issues.