ALASKA PIPELINE CO

Incident Narrative

INCIDENT: RELEASE OF GAS AT APC EAST ANCHORAGE GATE SITE DUE TO OVER PRESSURE ON 460 PSI SYSTEM DATE: SEPTEMBER 5, 2012 VOLUME RELEASED: 7.95 MILLION CUBIC FEET CHRONOLOGY OF EVENTS : WEATHER CONDITIONS: EXTREMELY HIGH WIND CONDITIONS IN EXCESS OF 120 MPH CAUSED NUMEROUS POWER OUTAGES AND SHUT DOWN OF POWER GENERATION STATIONS THROUGHOUT THE COOK INLET. TIMES ARE ESTIMATED +/- 2 MINUTES. 17:42 LOST POWER TO EAST ANCHORAGE GATE STATION ( EAG ) 17:42 SIGNIFICANT LOSS OF LOAD TO MLP POWER PLANT NUMBER 2 DUE TO FAULT CONDITIONS ON POWER SYSTEM 17:45 RELIEF OPENED ON 460 PSI SYSTEM AT EAST ANCHORAGE GATE DUE TO OVERPRESSURE 17:47 RELEASE OF GAS REPORT CALLED INTO ENSTAR (APC) DISPATCH 17:59 TECHNICIANS DISPATCHED TO EAG TO INVESTIGATE CAUSE 18:47 TECHNICIAN ON SITE AND CONTROLLED INCIDENT MITIGATING CIRCUMSTANCES APC'S EAG STATION INCLUDES A GAS DELIVERY SALES POINT TO MUNICIPAL LIGHT AND POWER'S STATION NUMBER 2. HIGH WINDS IN THE ANCHORAGE BOWL ON THE EVENING OF SEPTEMBER 5 CAUSED NUMEROUS POWER SYSTEM FAULTS TO OCCUR. THE POWER SYSTEM FED BY MLP 2 WAS INTERRUPTED DUE TO THE FAULT CONDITIONS, INTERRUPTING BOTH GENERATION AND ALSO POWER DELIVERY TO THE APC EAG STATION. BACK UP BATTERIES AT EAG WERE NOT CAPABLE OF CONTINUED SCADA SURVEILLANCE. ON IMMEDIATE CURTAILMENT OF GAS TO MLP 2, REGULATOR MALFUNCTION CAUSED THE 460 PSI SYSTEM TO OVERPRESSURE FOLLOWED BY OPENING OF THE OVERPRESSURE RELIEF. RESPONSE TIME WAS GREATER THAN WOULD NORMALLY BE EXPECTED DUE TO TRAFFIC CONDITIONS AGAIN CAUSED AGAIN TO LOSS OF POWER GENERATION.