TRANSCONTINENTAL GAS PIPE LINE COMPANY

Incident Narrative

ON MAY 3, 2016: STATION 90 EMPLOYEE'S WERE GREASING VALVES AT THE 90-10 VALVE SITE AND NOTICED THAT THERE WERE BUBBLES IN THE WATER ACCUMULATED AROUND GROUND LEVEL OF THE MAIN LINE BLOCK VALVE 90D10. MANAGER DUANE NELSON WAS ON SITE AT THE TIME OF DISCOVERY AND NOTIFIED PIPELINE CONTROL OF THE SMALL LEAK AT APPROXIMATELY 07:30 A.M. EMPLOYEE HAND DUG APPROXIMATELY ONE FOOT IN DEPTH BEFORE DETERMINING MORE EXCAVATION WAS NEEDED TO VERIFY THE LEAK SOURCE. MANAGER INSTRUCTED THE EMPLOYEE TO START LOWERING PRESSURE ON 'D' LINE FROM THE STATION 90D0 VALVE TO THE 90D20 VALVE SITE. AFTER LOWERING PRESSURE TO STATION 90 SUCTION PRESSURE (628 PSI), STATION 90 EMPLOYEES BEGAN EXCAVATION FOR FURTHER INVESTIGATION. AT APPROXIMATELY 9:39 A.M, THE INVESTIGATION REVELED THAT THE SOURCE OF THE LEAK WAS A FAILED VALVE BODY FLANGE O-RING SEAL. THE PIPELINE SEGMENT WAS CLOSED OFF AT STATION 90 AT APPROXIMATELY 11:00 A.M AND THE PRESSURE WAS DRAWN DOWN, AND THEN SHUT-IN BLOCK VALVE 90D20 AT 11:45 A.M. THE PIPELINE WAS ISOLATED FROM 90D0 TO 90D20 AND THE PRESSURE WAS LOWERED TO 627 PSI. THE SMALL LEAK WAS DETERMINED TO BE NON-HAZARDOUS. ON MAY 4, 2016: AFTER FURTHER REVIEW WITH OPERATIONS AND DISCUSSION WITH PIPELINE SAFETY, THE SMALL LEAK WAS DETERMINED TO BE AN INCIDENT BASED ON THE RECOMMENDED VALVE REPLACEMENT COST. PIPELINE CONTROL NOTIFIED THE NRC AT 10:14 A.M. OF THE SMALL 'O' RING LEAK ON TOP OF THE GATE VALVE BODY. THE VOLUME OF THE GAS RELEASED BY THE SMALL LEAK COULD NOT BE DETERMINED. ON MAY 9, 2016: GAS RECOMPRESSION SERVICE WAS COMMENCED AT 5:20 P.M. ON THE PIPELINE SEGMENT FOR THE PLANNED OUTAGE TO REMOVE AND REPLACE THE EXISTING 36-INCH DIAMETER GATE VALVE WITH A NEW BLOCK VALVE. ON MAY 13, 2016: RECOMPRESSION WAS COMPLETED TO A PRESSURE OF 111 PSI. ON MAY 19, 2016: THE PIPELINE SECTION WAS BLOWN DOWN TO 1 PSI . ON MAY 31, 2016: VALVE WAS REPLACED AND THE PIPELINE SECTION WAS PLACED BACK INTO SERVICE.