SOUTHWEST GAS CORP

Incident Narrative

DURING A LEAK SURVEY, SOUTHWEST GAS DISCOVERED A HAZARDOUS LEAK ON A 4-INCH ALDYL A MAIN AND 4-INCH ALDYL A SOCKET FUSION TEE AT 2398 SOUTH BOULDER HIGHWAY IN HENDERSON, NEVADA. THE FLOW OF GAS TO THE SECTION OF PIPE WAS DISCONTINUED IN ORDER TO COMPLETE THE REPAIR, RESULTING IN AN OUTAGE OF FIVE THOUSAND AND EIGHTY-ONE ACTIVE CUSTOMERS. THE COSTS OF SOUTHWEST GAS' EMERGENCY RESPONSE, LEAK LOCATING, FACILITY REPAIR AND SERVICE RESTORATION RESULTED IN THE INCIDENT MEETING PHMSA/DOT NOTIFICATION CRITERIA. PART A, 10: ESTIMATED VOLUME OF GAS RELEASED: 0.026 THOUSAND CUBIC FEET (MCF) PART C, 2A: YEAR 4-INCH ALDYL A MAIN INSTALLED, 1978 YEAR 4-INCH ALDYL A SOCKET FUSION TEE INSTALLED, 1984 PART G5: ADDITIONAL CAUSE: FUSION JOINT: 19. SPECIFY: SOCKET, HEAT FUSION 20. YEAR INSTALLED: 1984 21. OTHER ATTRIBUTES: 4-INCH ALDYL A 22A. FIRST MATERIAL BEING JOINED: POLYETHYLENE (PE) 22B. SECOND MATERIAL BEING JOINED: POLYETHYLENE (PE) 4-INCH ALDYL A MAIN - SLOW CRACK GROWTH RESULTING FROM PIPE DEFLECTION CREATING A STRESS CONCENTRATOR AT THE ENTRANCE TO THE SOCKET FUSED HEADER. 4-INCH ALDYL A SOCKET FUSION - SLOW CRACK GROWTH RESULTING FROM NON-FUSION FROM DEBRIS AT THE PIPE TO SOCKET FUSION INTERFACE AT THE PIPE END-POINT. THIS WAS DRIVEN BY PIPE DEFLECTION CREATING A STRESS CONCENTRATOR AT THE PIPE END-POINT INTERFACE WITH THE SOCKET-FUSED FITTING