ENABLE GAS TRANSMISSION, LLC

Incident Narrative

ON 10/24/2017 AN ENABLE MIDSTREAM EMPLOYEE DISCOVERED A RELIEF VALVE BLOWING AT THE AM-199 TO AM-47 INTERCONNECT FACILITY LOCATED IN THE RURAL PART OF MARION COUNTY. THE FACILITY IS APPROXIMATELY 1.4 MILES SOUTH OF AVINGER, TEXAS. LINE AM-199 HAS A MAOP OF 1000 PSIG AND IS A SOURCE FOR LINE AM-47, WHICH HAS A MAOP OF 500 PSIG UPON ARRIVAL AT THE STATION ON THE 10/24/2017, THE O&M TECHNICIAN STOPPED THE VENTING AND INSPECTED THE STATION. HE DISCOVERED THE CONTROLLER WAS FOUND TO HAVE A SET POINT OF 500 PSIG. THE O&M TECHNICIAN MOVED THE CONTROLLER BACK TO THE REQUIRED SET POINT (470 PSIG) AND TIGHTENED THE CONTROLLER ARM, WHICH WAS LOOSE. AFTER THE COMPLETION OF ALL WORK, A TEST GAGE WAS INSTALLED AND THE PRESSURE WAS MONITORED. THE STATION OPERATED NORMALLY AT THE 470 PSIG SET POINT FOR 30 MINUTES. THE NRC WAS NOTIFIED ON 10/24/2017 AT 11:45 (NRC# 1194155). A FOLLOW UP CALL WAS PROVIDED TO THE NRC ON 10/26/2017 AT 09:00 (NRC# 1194335). WHILE THIS LOCATION DOES NOT HAVE MEASUREMENT FACILITIES, THERE IS A MEASUREMENT STATION 20 MILES UPSTREAM AND ANOTHER 12 MILES DOWNSTREAM. STARTING OCTOBER 17TH, SYSTEM CONTROL REPORTED AN INCREASE IN FLOW OF GAS IN THIS AREA BUT COULD NOT LOCATE THE SOURCE OF THE IMBALANCE. SYSTEM CONTROL IMMEDIATELY NOTIFIED THE LOCAL OPERATIONS WHO SYSTEMATICALLY STARTED BACKTRACKING STATIONS AND TROUBLESHOOTING UNTIL THE VENTING RELIEF VALVE WAS DISCOVERED ON 10/24/17. THE FINAL GAS LOSS CALCULATION WAS DETERMINED BY THE MEASUREMENT GROUP FOR THE AREA WHO DETERMINED THE RELIEF VALVE BLEW INTERMITTENTLY FOR 14 DAYS UNTIL DISCOVERY ON 10/24/2017. DURING THE INVESTIGATION, IT WAS DETERMINED ENABLE O&M TECHNICIANS WERE TESTING REGULATORS AT THIS INTERCONNECT ON 10/10/2017. AN OUTAGE PREVENTION FORM WAS UTILIZED AND TEST GAUGE WAS INSTALLED TO MONITOR PRESSURE AT THE STATION WHILE TESTING. AT THE TIME OF THEIR ARRIVAL, THE CONTROLLER NEEDLE INDICATED A SET POINT OF APPROXIMATELY 420 PSIG. ALTHOUGH THE TEST GAUGE READ A PRESSURE OF 470 PSIG, THE SET POINT ON THE CONTROLLER WAS WITHIN THE REQUIRED RANGE AND NO ADJUSTMENTS WERE MADE. AFTER TESTING WAS COMPLETED AND WHILE LOADING TOOLS, THE O&M TECHNICIANS MONITORED THE PRESSURE AT THE REGULATOR STATION WITH A TEST GAGE. AFTER MONITORING PRESSURE FOR 20 MINUTES, A FINAL READING OF APPROXIMATELY 470 PSIG WAS READ AND THE TECHNICIANS LEFT THE REGULATOR STATION. ALTHOUGH THE INVESTIGATION CITED EQUIPMENT FAILURE AS THE MOST LIKELY CAUSE (MORE SPECIFICALLY THE LOOSE TENSION ON THE CONTROLLER ARM ALLOWING THE SET POINT TO MOVE), THE DECISION WAS MADE TO IMMEDIATELY SUSPEND, AND ULTIMATELY DISQUALIFY, THE TWO O&M TECHNICIANS ON THEIR OQ TASKS FOR TESTING REGULATORS AND CONTROL VALVES. THIS DECISION WAS BASED UPON THE FACT THEY WERE TESTING AT THE LOCATION THE DAY THE EVENT BEGAN ON 10/10/2017. THE OPERATORS WILL BE REQUIRED TO BE RE-OBSERVED ON THEIR TASKS. THE DECISION HAS ALSO BEEN MADE TO REPLACE THE BARTON CONTROLLER AT THE STATION, WHICH WAS INSTALLED IN 2007. UPDATE 11/17/2017 - A SUPPLEMENTAL REPORT WAS SUBMITTED TO CORRECT LINE DESIGNATION ERROR IN PART B.7 AND PART B.8 UPDATE 11/27/17 - A SUPPLEMENTAL REPORT WAS SUBMITTED WITH UPDATES MADE TO THE FOLLOWING SECTIONS: A.4, UPDATED DATE AND TIME TO REFLECT THE ESTIMATION OF THE RELEASE REACHING 3 MMCF A.10, UPDATED ESTIMATED VOLUME OF RELEASE A.19, UPDATED TO REFLECT WHEN SCADA INDICATIONS WERE RECOGNIZED BY CONTROLLER E.8, UPDATED TO REFLECT LANGUAGE FROM SYSTEM CONTROL INCIDENT INVESTIGATION REPORT G, CAUSE CHANGED TO INCORRECT OPERATION G.7, UPDATED TO INCORRECT OPERATION G.7.3-5, UPDATED DUE TO SELECTION OF INCORRECT OPERATION UPDATE 1/10/18 B.5 CHANGED COUNTY UPDATE 1/10/18 MARKED FINAL