GREAT LAKES GAS TRANSMISSION LIMITED PARTNERSHIP

Incident Narrative

ON JANUARY 12, 2024, SEVERE WEATHER INCLUDING HEAVY WINDS AND SNOW PASSED THROUGH THE GAYLORD, MICHIGAN AREA. WHEN THE POWER FAILURE ALARM WAS DETECTED, THE MONITORING CENTER CALLED THE TECHNICIAN ON SITE TO INVESTIGATE THE ALARM. THE TECHNICIAN COULD AUDIBLY HEAR BLOWING GAS AT 7:43 P.M. EST AND DISCOVERED NATURAL GAS WAS BEING RELEASED THROUGH THE UNIT 1101 BLOWDOWN STACK. IMMEDIATE ACTION WAS TAKEN BY VERIFYING NO FIRE EXISTED AND CLOSING THE UNIT VALVE WHICH ENDED THE RELEASE AT 8:15 P.M. EST. UNINTENTIONAL GAS LOSS WAS CALCULATED TO 3.61 MILLION CUBIC FEET (MMCF). NO PROPERTY DAMAGE, INJURIES OR MANDATORY EVACUATIONS WERE NEEDED. THE CAUSE OF THE UNINTENTIONAL RELEASE WAS ATTRIBUTED TO LOSS OF COMMERCIAL POWER AT THE STATION. THE BACKUP GENERATOR DID NOT START, AND THE VENT VALVE OPENED DUE TO THE LOSS OF CONTROL AIR PRESSURE. THE VENT VALVE IS DESIGNED TO FAIL OPEN IN THE CASE OF LOW CONTROL AIR AND THE SUCTION AND DISCHARGE VALVES REMAINED IN THEIR CURRENT OPEN OPERATING STATE. NO OVERPRESSURE OCCURRED. AFTER FURTHER INVESTIGATION OF THE AUXILIARY POWER UNIT (APU), IT WAS FOUND TWO LOOSE PRIMARY IGNITION WIRES CAUSED THE ENGINE TO BACKFIRE WHICH RESULTED IN A SMALL TEAR IN THE LEFT BANK SECONDARY FUEL REGULATOR DIAPHRAGM. A LOW HORSEPOWER CONDITION ENSUED. APU WAS REPAIRED AND PLACED BACK IN SERVICE ON JANUARY 19, 2024. MODIFIED SECTIONS A5, G2 AND G6 PER PHMSA'S REQUEST.