PACIFIC GAS & ELECTRIC CO

Incident Narrative

ON JANUARY 7, 2015 AT 1704 HOURS IN ARVIN, AN 8-INCH PRESSURE RELIEF VALVE (AT PRESSURE LIMITING STATION,4-PLS OFF OF TRANSMISSION LINE L-300B) OPENED PRIOR TO REACHING ITS SET POINT OF 749 PSIG RESULTING IN AN UNINTENTIONAL RELEASE OF NATURAL GAS TO THE ATMOSPHERE. THE PRESSURE IN L-300B AT THE TIME THE RELIEF VALVE OPERATED WAS 720 PSIG. THE INCIDENT WAS IDENTIFIED ON PG&E'S SCADA SYSTEM. IN RESPONSE, PG&E GAS CONTROL REMOTELY LOWERED THE PRESSURE IN L-300B BY LOWERING THE SETPOINT OF THE UPSTREAM REGULATOR TO 675 PSIG, WHICH ALLOWED THE PRESSURE RELIEF VALVE TO CLOSE AT 1710 HOURS. PG&E PERSONNEL ARRIVED ON SCENE AT 1745 HOURS AND THE VALVE'S SET POINT OF 749 PSIG WAS TESTED AND VERIFIED. 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. NO CUSTOMERS LOST GAS SERVICE DURING THE INCIDENT. PRESSURE IN L-300B DID NOT EXCEED THE MAOP OF 757 PSIG. THERE WERE NO INJURIES, NO FATALITIES AND NO MEDIA OBSERVED ON SCENE DURING THE INCIDENT. ON JANUARY 9, 2015, IT WAS ESTIMATED THAT THE VOLUME OF GAS RELEASED EXCEEDED 3 MILLION CUBIC FEET (MMCF), THEREFORE THE INCIDENT WAS REPORTED TO THE NATIONAL RESPONSE CENTER AND THE CPUC. (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 UPSTREAM REGULATOR, WHICH ALLOWED THE PRESSURE RELIEF VALVE TO CLOSE. THE PHMSA 7100 REPORT FORM DOES NOT ALLOW THESE FIELDS TO BE LEFT BLANK.)