Respondent owns and operates a disposal facility associated process equipment. At the facility the Respondent stored produced water, including residual hydrocarbons, in a 500-barrel fiberglass tank. Produced water stored in this tank was generated from multiple wells. Produced waters, and their associated vapors, are extremely hazardous substances due to their flammability and explosive nature. On November 26, 2014, a two man contractor crew cut an existing four inch fiberglass inlet collar and began to install a neck tank collar. Instead of allowing the repair to naturally “cold cure” a heat gun was used to accelerate the fiberglass curing process. Flammable hydrocarbon vapors from the produced water tank and a disconnected vent line ignited, causing a fire and destruction of the produced water tank and damage to the rest of the disposal facility. The two contractor crew members were treated for burns and various broken bones from jumping from the burning tank, and they were subsequently released from medical care.