COLUMBIA GAS TRANSMISSION, LLC

Incident Narrative

LINE 1547 IS A 14-IN STEEL, BARE CATHODICALLY PROTECTED TRANSMISSION PIPE THAT IS OWNED, OPERATED AND MAINTAINED BY COLUMBIA GAS TRANSMISSION, LLC (COLUMBIA). ON APRIL 23, 2015, AT 10:43 AM, A COLUMBIA COMPRESSOR STATION (CS) OPERATOR HEARD A NOISE TO THE NORTHWEST OF HIS LOCATION. UPON VISUALLY CHECKING THE SOURCE OF THE NOISE, THE CS OPERATOR OBSERVED A CLOUD OF DUST BLOWING INTO ATMOSPHERE. HE THEN IMMEDIATELY OBSERVED A DROP IN PRESSURE IN LINE 1547 WHICH IS ON THE DISCHARGE SIDE OF THE CS. THE CS OPERATOR CLOSED THE VALVES TO ISOLATE AND STOP THE FLOW OF MATERIAL THROUGH LINE 1547, THEN CONTACTED THE PROPER COLUMBIA PERSONNEL REQUESTING LOGISTICAL AND LOCATION ASSESSMENT AND CONFIRMATION SUPPORT. COLUMBIA PERSONNEL CONFIRMED THE INCIDENT INVOLVED LINE 1547 WHICH WAS NOTED BY FIRST RESPONDERS TO HAVE SEPARATED AT THE GIRTH WELD. AT THE TIME OF THE FAILURE, LINE 1547 WAS IMMEDIATELY ADJACENT TO A 16-IN DIAMETER LINE THAT WAS UNDER CONSTRUCTION AND INTENDED TO REPLACE THE EXISTING 14-IN LINE AS PART OF COLUMBIA S PLANNED CONSTRUCTION PROGRAM. SINCE CONSTRUCTION OF LINE 1547 WAS ALREADY WELL UNDERWAY, COLUMBIA DECIDED TO ABANDON THE FAILED 14-IN PIPE AND FINISH THE CONSTRUCTION OF THE REPLACEMENT LINE RATHER THAN BRING OLD LINE 1547 BACK INTO SERVICE. SEGMENTS OF THE FAILED PIPE WERE SENT TO A CONTRACTED METALLURGICAL FAILURE ANALYSIS CONSULTANT FOR A ROOT CAUSE ANALYSIS FAILURE DETERMINATION. FURTHERMORE, A GEOTECHNICAL ASSESSMENT OF THE IMMEDIATE AREA AFFECTING BOTH LINES (THE 14-IN PIPE AND THE NEW 16-IN PIPE) WAS PERFORMED AND STRAIN GAUGES WERE INSTALLED ONTO THE NEW 16-IN PIPELINE FOR MONITORING ANY POTENTIAL FUTURE STRESSES. FINALLY, AN INTEGRITY ASSESSMENT WAS PERFORMED TO THE NEW 16-IN PIPE 1547 LINE. CONSTRUCTION WAS COMPLETED ON THE NEW 16-IN REPLACEMENT PIPELINE AND LINE 1547 WAS PLACED INTO SERVICE ON MAY 14, 2015.THE NEWLY CONSTRUCTED 16-IN LINE PIPE WAS CONSTRUCTED AND WAS PUT IN SERVICE AS OF MAY 14, 2015. THE METALLURGICAL FAILURE ANALYSIS REPORT OF THE 14-IN PIPE IDENTIFIED THE FOLLOWING: THE PIPELINE FAILURE WAS INITIATED AT THE GIRTH WELD, WHERE INCOMPLETE PENETRATION (IP) WELD DEFECTS WERE PRESENT. THERE WAS NO EVIDENCE OF IN-SERVICE GROWTH OF THE IP DEFECTS. HIGH AXIAL TENSILE STRESSES ACTING ON THE GIRTH WELD WERE LIKELY TO BE CONSIDERED AS CONTRIBUTING FACTORS IN THE PIPELINE FAILURE.