BLACK HILLS ENERGY

Incident Narrative

AT APPROXIMATELY 1722 AURORA VOLUNTEER FIRE DEPARTMENT (AVFD) WAS CALLED TO 1501 'A' STREET IN AURORA NE FOR A FIRE. THIS IS A HAMILTON COUNTY HIGHWAY DEPARTMENT COMPLEX. FIRE LOCATED WITHIN THE 'BRIDGE BUILDING' AVFD EXTINGUISHED THE FIRE AND DURING OVERHAUL DISCOVERED VAPOR ESCAPING THROUGH CRACKS IN THE FLOOR OF STRUCTURE. THE GAS OPERATOR BLACK HILLS ENERGY (BHE) WAS CONTACTED REGARDING FIRE AT 1853 HOURS. STATE FIRE MARSHAL INVESTIGATOR DETERMINED THE PRODUCT TO BE NATURAL GAS AT 1915 HOURS THE GAS OPERATOR WAS INFORMED OF PROBABLE INVOLVEMENT OF NATURAL GAS AT 1936 AND TO STOP THE FLOW OF NATURAL GAS TO AREA. FIRST BHE PERSONNEL ARRIVED AT LOCATION 1946 HOURS ADDITIONAL BHE PERSONNEL RESPONDED TO LOCATION AND EXCAVATED THE SERVICE LINE, EXPOSING THE SERVICE LINE, CUT AND CAPPED THE SERVICE LINE. GAS FLOW STOPPED AT 2245 HOURS. IT WAS DISCOVERED THAT NATURAL GAS FROM A FAILED UNDERGROUND PIPE HAD VENTED ITSELF INSIDE THE STRUCTURE. NATURAL GAS LEVELS INSIDE THE STRUCTURE INCREASED TO AN IGNITABLE LEVEL, IGNITION WAS PROVIDED BY A GAS FIRED OVERHEAD UNIT HEATER WITH STANDARD SAFETY PILOT. THE NATURAL GAS FLASHED ACROSS THE ROOM AND BACK TO THE CRACKS IN THE FLOOR WHERE IT CONTINUED TO BURN, IGNITING COMBUSTIBLE MATERIALS BELOW WORK BENCHES ALONG THE EAST AND WEST WALLS. ON 3/5/13 GAS DEPARTMENT CREW EXCAVATED AN AREA NEAR A TEE JUNCTION IN THE SERVICE LINE REVEALING A MECHANICAL FITTING. VISUALLY APPARENT WAS THE FACT THAT A SEGMENT OF 3/4' DUPONT ALDYL-A PE PIPING HAD PULLED OUT OF THE MECHANICAL FITTING APPROXIMATELY 3/4', ALLOWING GAS TO FLOW UNRESTRICTED UNDERGROUND. THE MECHANICAL FITTING WAS REMOVED AND REMAINING PIPE SEGMENTS AIR TESTED AND DETERMINED TO BE LEAK FREE. NATURAL GAS UNDERGROUND PIPING WITHIN THE COMPLEX WAS REPLACED.