INTERMOUNTAIN GAS CO

Incident Narrative

INTERMOUNTAIN GAS COMPANY (IGC) WAS NOTIFIED OF AN OUTSIDE GAS ODOR IN GOSHEN, ID (AN UNINCORPORATED COMMUNITY IN BINGHAM COUNTY) AT 18:07 ON FEBRUARY 27, 2021. AFTER ARRIVING ON SITE AT 18:51, A COMPANY FIRST RESPONDER FOUND A 3"" RELIEF VALVE AT A DISTRICT REGULATOR IN THE FULL OPEN POSITION AT WHICH TIME ADDITIONAL PERSONNEL WAS DISPATCHED TO THE SCENE. THE REGULATORS AT THE LOCATION OF THE RELIEF VALVE WERE INSPECTED AND FOUND TO BE OPERATING CORRECTLY. COMPANY PERSONNEL THEN BEGAN INSPECTING THE REGULATORS AT A REGULATOR STATION LOCATED 3.7 MILES WEST OF THE BLOWING RELIEF VALVE THAT SUPPLIES GAS TO THE SAME 200 PSIG MAOP PIPELINE. THE PRIMARY REGULATOR AT THE SECOND REGULATOR STATION WAS SHUT IN AT 21:45 AT WHICH TIME THE SYSTEM PRESSURE DROPPED TO 170 PSIG; HOWEVER, THE RELIEF VALVE WAS STILL IN THE OPEN POSITION. THE RELIEF VALVE WAS ISOLATED AT 12:28 ON FEBRUARY 28, 2021. IT WAS DETERMINED HYDROCARBONS HAD ACCUMULATED AND FROZE CAUSING THE RELIEF VALVE TO STICK IN THE OPEN POSITION. THE MORNING OF MARCH 1, 2021 COMPANY PERSONNEL INSPECTED AND REPAIRED THE PRIMARY REGULATOR AT THE SECOND REGULATOR STATION. A YELLOW/WHITE POWDER WAS FOUND ON THE SEAT, DIAPHRAGM AND PILOT COMPONENTS WHICH WAS THE CAUSE OF THE REGULATOR FAILURE THAT RESULTED IN THE RELIEF VALVE OPENING. THE POWDER WAS CLEANED OFF ALL SURFACES AND THE SOFT COMPONENTS WERE REPLACED. AT 11:52 ON MARCH 1, 2021 THE ENGINEERING DEPARTMENT CALCULATED THE GAS LOSS FOR THIS RELEASE AT WHICH TIME IT WAS DISCOVERED THE 3 MILLION CUBIC FEET REPORTING THRESHOLD WAS EXCEEDED.