TRANSCONTINENTAL GAS PIPE LINE COMPANY

Incident Narrative

TIMELINE FOR TRANSCO STATION 535 INCIDENT: 12/12/2016 ALL TIMES ARE EST 3:07 PM: 20 GAS PIPELINE LEADING TO DEHYDRATORS EXPERIENCES A FAILURE RESULTING IN A RUPTURE AND FIRE. 3:08 PM: PLANT PERSONNEL ESD THE STATION AND PERSONNEL EVACUATE TO MUSTER POINT 3:11 PM: LOCAL FIRE DEPARTMENTS RECEIVED NOTIFICATION 3:15 PM: LOCAL RESPONDERS DISPATCHED 3:17 PM: WILLIAMS SECURITY OPERATIONS CENTER NOTIFIED. 3:40PM: LOCAL FIRE DEPARTMENT ARRIVE 4:00 PM: NRC NOTIFICATION COMPLETED 4:30 EMERGENCY SERVICES CONTROLLING FROM OUTSIDE FENCE AND ALL OPERATIONS PERSONNEL ACCOUNTED FOR AND NO REPORTED INJURIES. 6:55PM: MAIN FIRE EXTINGUISHED AND LINES AFFECTED ISOLATED, FUEL GAS LINE WAS CONTROLLED BURN AND DECISION WAS MADE TO LET IT BURN OVERNIGHT. 8:23PM: LOCAL FIRE DEPARTMENTS LEAVE SITE 12/13/2016 APPROXIMATE 11:00: FIRE FROM FUEL GAS LINE EXTINGUISHED. ADDITIONAL INFORMATION / ADDITIONAL ROOT CAUSES: THE INCIDENT INVESTIGATION AND ASSOCIATED ANALYSIS PROVIDED THE CONCLUSION THAT INTERNAL CORROSION CAUSED THE PIPING RUPTURE. THINNING OF THE PIPE WALL WAS CAUSED BY SALT WATER CORROSION, ULTIMATELY LOWERING RUPTURE RESISTANCE. ON NOVEMBER 19, 2015, EMPLOYEES AT STATION 535 DISCOVERED GAS LEAKING UP THROUGH THE GROUND IN THE STATION YARD AND UPON FURTHER INVESTIGATION DETERMINED THE SOURCE TO BE THE 20 INCH UNDERGROUND LINE ON THE INLET SIDE OF STATION'S DEHYDRATION. THIS LINE WAS BLOWN DOWN AND TAKEN OUT OF SERVICE AS PLANS WERE PUT INTO PLACE FOR REPAIRS. IT WAS IMMEDIATELY CONFIRMED THAT THE LEAK WAS CAUSED BY INTERNAL CORROSION. THE REPAIR CONSISTED OF REMOVING CORRODED PIPING UNTIL PIPING OF SUFFICIENT INTEGRITY WAS FOUND TO TIE NEW PIPING BACK INTO. THIS REPAIR WORK WAS ALSO USED AS AN OPPORTUNITY TO REMOVE DEAD HEADS AND OTHER PIPING IN THE IMMEDIATE VICINITY THAT WERE NO LONGER USED OR NOT NEEDED FOR THE PROCESS. THE STATION WAS OUT OF SERVICE FOR APPROXIMATELY 6 WEEKS IN AN EFFORT TO IDENTIFY AND REPAIR AREAS OF CONCERN. IT WAS RECOGNIZED THAT ADDITIONAL DEAD HEADS EXISTED IN THE STATION AND A PROJECT WAS PLANNED FOR 2016 TO INVESTIGATE OTHER POTENTIAL DEAD HEADS FOR INTERNAL CORROSION. THE 2016 PROJECT WAS DELAYED TO COINCIDE WITH A COMPREHENSIVE PLANNED MECHANICAL INTEGRITY ASSESSMENT OF THE STATION VESSELS AND BELOW GROUND PIPING IN 2017. THE UNDERGROUND PIPING IN THE YARD AND ABOVE GROUND HEADERS HAVE BEEN REPLACED. A FEW PIPES CONNECTING TO NATIONAL FUEL GAS WERE INSPECTED AND LEFT IN PLACE. THE DEHYDRATORS HAVE BEEN REMOVED AND REPLACED. FILTER SEPARATORS HAVE BEEN INSPECTED. GAS WAS INJECTED INTO THE SYSTEM ON 02/27/2019.