GREAT LAKES GAS TRANSMISSION LIMITED PARTNERSHIP

Incident Narrative

ON MARCH 6TH AT 12:37 EST, GLGT GAS CONTROL RECEIVED AN EMERGENCY SHUTDOWN SYSTEM (ESD) VALVE OUT OF POSITION ALARM, AT WAKEFIELD COMPRESSOR STATION LOCATED AT 400 GREAT LAKES ROAD, WAKEFIELD, MI 49968, (46.43969, -89.83737). WHEN THE ALARM WAS DETECTED, A TECHNICIAN WAS DISPATCHED TO THE COMPRESSOR STATION TO INVESTIGATE. UPON ARRIVAL AT THE SITE AT 13:50 EST, THE TECHNICIAN DISCOVERED NATURAL GAS BEING RELEASED TO THE ATMOSPHERE THROUGH THE EIGHT-INCH VENT STACK. IMMEDIATE ACTION WAS TAKEN BY VERIFYING NO EMERGENCY EXISTED AND CLOSED THE VALVE, WHICH ENDED THE RELEASE AT 14:14 EST. UNINTENTIONAL GAS LOSS WAS CALCULATED TO APPROXIMATELY 40.7 MILLION CUBIC FEET (MMCF). INVESTIGATION INDICATED THAT THE SYSTEM VENT VALVE (Y-01-DE) FAILED DUE TO A SOLENOID FAILURE THAT HOLDS THE ESD VALVE CLOSED WHICH CONTRIBUTED TO THE GAS LOSS. ADDITIONALLY, AN AUTOMATIC ISOLATION VALVE (Y-02-D) FAILED TO COMPLETELY CLOSE DUE TO ICE ACCUMULATION FREEZING THE VALVE IN THE OPEN POSITION RESULTING IN THE CONTINUING RELEASE OF GAS TO THE ATMOSPHERE THROUGH THE 8-INCH VENT STACK. BOTH SOLENOIDS WERE REPLACED ON MARCH 7TH, 2022. THE ESD SYSTEM HAS BEEN INSPECTED AND TESTED ACCORDING TO PROCEDURES AND OPERATED CORRECTLY. THE SYSTEM HAS BEEN PLACED BACK INTO FULL-SERVICE MARCH 7TH AT 18:00 EST.