If you are able to degas your sulfur to meet EPA limits, you may be able to store it onsite. Otherwise you will definitely have an SO2 emissions exceedence by exposing tons of molten sulfur to atmosphere. As previously mentioned, check with your local regulatory agency before changing your operation. Elemental sulfur by itself is generally not considered an environmental problem as it is very slow to dissolve in water. There may also be short term vs long term storage requirements to comply with that may require you to remove your emergency pile.