SOUTHWEST GAS CORP

Incident Narrative

SOUTHWEST GAS (COMPANY) CONSTRUCTION CREWS WERE PERFORMING MAINTENANCE TO REPLACE A 4-INCH PE VALVE, THAT HAD A PREVIOUSLY DISCOVERED NON-HAZARDOUS GRADE 2 LEAK, AND HIT A 4-INCH PE GAS LINE WITH A BACKHOE DURING EXCAVATION. PART A, 16: FIRE DEPARTMENT CONDUCTED A PRECAUTIONARY EVACUATION OF 30 OCCUPANTS AS A RESULT OF THE FIRE. PART C, 5: THE DAMAGE TO THE 4-INCH PE MAIN WAS EXTENSIVE AS A RESULT OF THE IGNITION AND SUBSEQUENT FIRE; THEREFORE, THE SIZE OF THE PUNCTURE COULD NOT BE DETERMINED. THE ESTIMATED VOLUME OF GAS RELEASED WAS CALCULATED ASSUMING A FULL 4-INCH CIRCUMFRENTIAL BREAK. PART G3, 11: SEVERAL NON-GAS UTILITIY LINE MARKINGS WERE VISIBLE IN THE AREA THE COMPANY DELINEATED FOR EXCAVATION, INCLUDING WATER, POWER AND STREET LIGHTING. COMPANY PERSONNEL DID NOT SUFFICIENTLY LOCATE AND MARK ALL OF THE GAS FACILITIES WITHIN THE DELINEATED AREA IN ACCORDANCE WITH ITS LINE LOCATING PROCEDURES. AS A RESULT OF THE COMPANY'S INVESTIGATION TO DATE, THE COMPANY BELIEVES THAT IF ITS LINE LOCATING PROCEDURES WERE FOLLOWED A DISCREPANCY IN THE ALIGNMENT OF THE FACILITY WOULD HAVE BEEN IDENTIFIED BETWEEN THE MAP, ASBUILT AND THE ACTUAL FIELD FACILITY LOCATION. PART G3, 14: IN ADDITION TO THE PRIMARY CAUSE OF INSUFFICIENT LOCATING PRACTICES THE COMPANY IDENTIFIED AN ADDITIONAL CONTRIBUTING CAUSE. THE EXCAVATION DAMAGE OCCURRED AT OR NEAR AN UNMAPPED AND NON-LOCATED 4-INCH 45 DEGREE ELBOW THAT DID NOT APPEAR ON AS-BUILT DOCUMENTATION. THE EXCAVATION DAMAGE IS BELIEVED TO HAVE OCCURRED ON A PORTION OF THE PIPE THAT CHANGED DIRECTION BECAUSE THE 4"" PE MAIN AND VALVE WERE EXPOSED AND BEING SPOTTED BY COMPANY EMPLOYEES WHILE THE BACKHOE OPERATOR WAS REMOVING DIRT ADJACENT TO THE PIPELINE FACILITY.