SOUTHERN NATURAL GAS CO

Incident Narrative

10/25/2016; 3:50 AM, EMPLOYEE WHO LIVES NEAR THE COMPRESSOR STATION, AWAKENED BY A NOISE, CALLED GAS CONTROL; EMPLOYEE LEARNS THERE IS AN ESD ALARM AND THE COMPRESSOR STATION IS RUNNING; EMPLOYEE LEAVES HOME TO CHECK THE COMPRESSOR STATION; WHILE IN ROUTE EMPLOYEE CALLS OTHER EMPLOYEES TO COME ASSIST AS NEEDED; EMPLOYEE ARRIVES AT COMPRESSOR STATION AT 3:58 AM AND FINDS ENGINES RUNNING AND THREE STATION YARD BLOW-OFFS VENTING; 4:03 AM GAS CONTROL CONFIRMS OTHER EMPLOYEES ARE IN ROUTE; 4:05 AM ANOTHER EMPLOYEE ARRIVES AT COMPRESSOR STATION; 4:06 AM EMPLOYEES BEGIN TAKING COMPRESSOR ENGINES OFF-LINE; 4:07 AM AS THE FIRST ENGINE WAS BEING TAKEN OFF-LINE, ALL REMAINING ENGINES WERE IMMEDIATELY SHUT DOWN BY THE STATION CONTROL SYSTEM; WITH ALL ENGINES SHUT DOWN, EMPLOYEES BEGIN TO ADJUST VALVES AS NEEDED TO BYPASS STATION; IN DOING SO EMPLOYEES NOTICE TWO 8-INCH STATION YARD BLOW-OFFS HAD STOPPED VENTING; EMPLOYEES FOUND MAIN LINE VALVES IN THE STATION YARD HAD PROPERLY OPENED FOR STATION BYPASS DURING THE EVENT AND NEEDED NO INTERVENTION; 4:25 AM EMPLOYEES CLOSED STATION VALVES WHICH CEASED THE GAS SUPPLY TO A 4-INCH STATION YARD BLOW-OFF; AT THIS TIME, EMPLOYEES THOUGHT THE GAS RELEASE WAS BELOW 3,000 MCF; AS PERSONNEL BECAME AVAILABLE TO CONSULT, MANAGERS DISCUSSED THE EVENT AND DETERMINED THE GAS RELEASE COULD BE A REPORTABLE VOLUME AND BEGAN CONTACTING OTHERS FOR INFORMATION AND REPORTING PURPOSES; 6:29 AM NRC TELEPHONE NOTIFICATION; DURING AND AFTER THE EVENT, CLARKE COUNTY, MISSISSIPPI EMA EMPLOYEES CONTACTED SNG EMPLOYEES CONCERNING THE EVENT AS THEY HAD RECENT TRAINING WITH A SNG EMPLOYEE; THE COMPRESSOR STATION RETURNED TO SERVICE 10/25/2016, 6:30 AM; INVESTIGATION LED TO THE INSTALLATION OF REBUILD KITS IN THE PILOT VALVE AND MANUAL SELECTOR BLOCK OF A CONTROL VALVE OPERATOR AS A SMALL LEAK IN EITHER COMPONENT WOULD HAVE CAUSED THE EVENT; REPAIR ALSO INCLUDED REPLACEMENT OF SAID VALVE OPERATOR'S ESD SWITCH.