PACIFIC GAS & ELECTRIC CO

Incident Narrative

ON NOVEMBER 22, 2014 AT 1652 HOURS AN 8-INCH PRESSURE RELIEF VALVE ON PG&E'S 34-INCH TRANSMISSION LINE L-300B AT PRESSURE LIMITING STATION 4-PLS MALFUNCTIONED RESULTING IN AN UNINTENTIONAL RELEASE OF NATURAL GAS TO THE ATMOSPHERE. PG&E PERSONNEL ARRIVED ON SCENE AT 1741 HOURS AND THE RELEASE OF GAS WAS STOPPED AT 1948 HOURS BY CLOSING TWO BRIDAL VALVES, WHICH ISOLATED THE RELIEF VALVE, ALLOWING GAS TO BYPASS THE RELIEF VALVE THROUGH A MAINLINE VALVE ON THE TRANSMISSION LINE. NO CUSTOMERS EXPERIENCED GAS SERVICE INTERRUPTION. THERE WERE NO INJURIES, NO FATALITIES AND NO IGNITION AS A RESULT OF THIS INCIDENT. A LOCAL RESIDENTIAL CLUBHOUSE WAS EVACUATED BY THE FIRE DEPARTMENT OUT OF AN ABUNDANCE OF CAUTION. LOCAL MEDIA WAS ON SCENE DURING THE INCIDENT. THE PRESSURE RELIEF VALVE (PRV) INSTRUMENTATION TUBING WAS REPLACED, ITS SET POINTS WERE RE-TESTED, AND A FUNCTIONAL CHECK OUT WAS COMPLETED BY DECEMBER 10, 2014. PRIOR TO REPAIRING THE MALFUNCTIONING PRV, OVERPRESSURE PROTECTION WAS PROVIDED BY CONTROLLING AND RESTRICTING THE NATURAL GAS PRESSURE THROUGH 3-PLS (THE PRESSURE LIMITING STATION UPSTREAM OF 4-PLS.) FOLLOWING THE INCIDENT, PG&E CONTRACTED A THIRD PARTY ENGINEERING FIRM TO PERFORM A ROOT CAUSE ANALYSIS AND PROVIDE RECOMMENDATIONS TO THE STATION. PG&E IMPLEMENTED SEVERAL MODIFICATIONS AND IS CURRENTLY IN THE DESIGN PHASE TO REBUILD PLS-4. PG&E INSPECTS AND CALIBRATES PRESSURE RELIEF VALVES (PRV) AS PART OF PG&E'S ROUTINE MAINTENANCE PROGRAM, WHICH IS DESIGNED TO ENSURE THE RELIABLE OPERATION OF THIS EQUIPMENT AT PG&E'S PRESSURE LIMITING STATIONS. THE UNINTENTIONAL RELEASE OF NATURAL GAS IS ESTIMATED TO BE APPROXIMATELY 119 MILLION CUBIC FEET (MMCF), THEREFORE THE INCIDENT WAS REPORTED TO THE DOT AND CPUC.