MIDAMERICAN ENERGY COMPANY

Incident Narrative

ON OCTOBER 18, 2010, AT 18:23, A FIRE AND EXPLOSION OCCURRED AT THE SIOUX CITY LIQUID PROPANE PLANT IN SIOUX CITY, IOWA. TWO EMPLOYEES WERE ISOLATING AND VENTING THE PLANT SEND-OUT PIPING IN PREPARATION FOR PIPE MODIFICATION. THE PRODUCT BEING VENTED WAS PROPANE. BECAUSE OF THE LOCATION OF THE VENTING, PROPANE LIQUID AND VAPOR ACCUMULATED. THE VAPOR WAS IGNITED BY AN ELECTRICAL SOURCE IN AN UNOCCUPIED ROOM CAUSING AN EXPLOSION AND FIRE. THE EXPLOSION COMPROMISED THE VAPOR BARRIER BETWEEN THE ELECTRONIC EQUIPMENT AND THE MIXER ROOM, AND FIRE IGNITED PROPANE VAPORS THAT HAD ACCUMULATED IN THE MIXER ROOM. THE BUILDING AND ELECTRONIC EQUIPMENT SUSTAINED SIGNIFICANT DAMAGE. THE INCIDENT INVOLVED THE RELEASE OF PROPANE, FIRE, EXPLOSION AND PROPERTY DAMAGE EXCEEDING $50,000. THEREFORE, THE INCIDENT WAS REPORTABLE AS REQUIRED BY PIPELINE HAZARDOUS MATERIAL SAFETY ADMINISTRATION RULES 49 CFR 191.3. THERE WERE NO INJURIES AND NO DEATHS. THE ON-SITE PAINTING CONTRACTOR EMPLOYEES THAT WERE WORKING SEVERAL HUNDRED FEET FROM THE INCIDENT ALSO EVACUATED THE PLANT WITHOUT INJURY. THE LOCAL FIRE DEPARTMENT RESPONDED, AND POLICE BLOCKED THE PUBLIC ROAD PASSING IN FRONT OF THE PLANT. THERE WAS EXTENSIVE MEDIA COVERAGE.