PACIFIC GAS & ELECTRIC CO

Incident Narrative

ON MAY 13, 2016 AT 1445 HOURS AN 8-INCH PRESSURE RELIEF VALVE (AT PRESSURE LIMITING STATION PLS4, OFF OF TRANSMISSION LINE L-300A) IN ARVIN, KERN COUNTY, MALFUNCTIONED RESULTING IN AN UNINTENTIONAL RELEASE OF GAS TO THE ATMOSPHERE. THE APPARENT CAUSE OF THE RELIEF VALVE MALFUNCTION WAS DUE TO EXCESS VIBRATION. PRESSURE IN L-300A DID NOT EXCEED THE MAOP OF 757 PSIG. OPERATION OF THE PRESSURE RELIEF VALVE WAS OBSERVED ON SCADA BY GAS CONTROL ROOM PERSONNEL AT THE TIME OF THE RELEASE, SO THE MAIN LINE REGULATOR SET POINT WAS REMOTELY LOWERED WHICH ALLOWED THE PRESSURE RELIEF VALVE TO RE-SEAT ITSELF. PG&E PERSONNEL WERE ON-SCENE AT 1740 HOURS AND THE RELEASE OF GAS WAS STOPPED AT 1800 HOURS BY REPLACING THE PILOT VALVE. THERE WERE NO INJURIES, NO FATALITIES, NO MEDIA AND NO IGNITION ASSOCIATED WITH THIS INCIDENT. THERE WAS NO CUSTOMER IMPACT. A NOTIFICATION WAS MADE TO THE NRC ON MAY 14, 2016 AT 1315 HOURS; ONCE IT WAS DETERMINED THE UNINTENTIONAL RELEASE OF GAS WAS ESTIMATED TO BE ABOVE 3 MILLION CUBIC FEET (MMCF). THE TOTAL ESTIMATED VOLUME RELEASE IS APPROXIMATELY 7.99 MMCF. LOCAL AGENCIES WERE NOTIFIED SEPARATELY ON MAY 13, 2016 BY PG&E'S ENVIRONMENTAL GROUP. THIS INCIDENT WAS REPORTED TO THE DOT & CPUC BECAUSE OF THE VOLUME OF GAS UNINTENTIONALLY RELEASED WAS ESTIMATED TO EXCEED 3 MMCF. A SPECIAL LEAK SURVEY WAS CONDUCTED FOLLOWING THE INCIDENT, AND NO LEAKS WERE IDENTIFIED.