PACIFIC GAS & ELECTRIC CO

Incident Narrative

AT APPROXIMATELY 0348 HOURS ON JANUARY 28, 2015 AN 8-INCH PRESSURE RELIEF VALVE (AT PRESSURE LIMITING STATION,4-PLS OFF OF TRANSMISSION LINE L-300B) IN ARVIN OPENED PRIOR TO REACHING ITS SET POINT RESULTING IN AN UNINTENTIONAL RELEASE OF NATURAL GAS TO THE ATMOSPHERE. PRESSURE IN L-300B 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 AND NATURAL GAS RELIEVING TO ATMOSPHERE WAS STOPPED AT 0408 HOURS. PG&E PERSONNEL ARRIVED ON SITE AT 0645 HOURS. THERE WERE NO INJURIES, NO FATALITIES AND NO MEDIA OBSERVED ON SCENE DURING 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. THIS INCIDENT WAS REPORTED TO DOT & CPUC BECAUSE THE ESTIMATED VOLUME OF NATURAL GAS RELEASED WAS ESTIMATED ABOVE 3 MILLION CUBIC FEET (MMCF). PG&E LATER CONFIRMED THAT APPROXIMATELY 15.2 MMCF WAS UNINTENTIONALLY RELEASED. (PLEASE NOTE THAT THE RESPONSES TO PART E, QUESTIONS 5A, 5B, AND 5C OF THIS PHMSA 7100 REPORT ARE MERELY PLACEHOLDERS AND DO NOT APPLY. PG&E GAS CONTROL REMOTELY LOWERED THE PRESSURE IN L-300B BY LOWERING THE SETPOINT OF THE MAIN LINE REGULATOR, WHICH ALLOWED THE PRESSURE RELIEF VALVE TO CLOSE. THE PHMSA 7100 REPORT FORM DOES NOT ALLOW THESE FIELDS TO BE LEFT BLANK.)