COLUMBIA GAS TRANSMISSION CORP

Incident Narrative

ON DECEMBER 5, 2013, A MILLENNIUM PIPELINE COMPANY (MPC) CONTRACTOR WAS INSTALLING A STOPPLE ON A 30-IN PIPELINE TO ENABLE THE NEWLY CONSTRUCTED COMPRESSOR STATION (HANCOCK) TO TIE-IN TO THE 30-IN MAINLINE PIPE. A NUISANCE LEAK WAS IDENTIFIED AT THE WEST STOPPLE WELDED TEE BY A CONTRACTOR EMPLOYEE. COLUMBIA GAS TRANSMISSION (COLUMBIA) WHO OPERATES AND MAINTAINS MPC'S PIPELINE, INVESTIGATED THE LEAK. PLANS BY ENGINEERING AND FIELD OPERATIONS PERSONNEL WERE SET IN MOTION TO RECTIFY THE NUISANCE LEAK. A DECISION BY COLUMBIA ENGINEERING SERVICES AND FIELD OPERATIONS PERSONNEL WAS MADE TO REDUCE THE OPERATING PRESSURE TO A SAFE VALUE TO 20% OF ITS CURRENT OPERATING PRESSURE AND PERFORM FOLLOW-UP NON-DESTRUCTIVE TESTING (NDT) TO THE IDENTIFIED LOCATION OF THE LEAK. LINE OPERATING PRESSURE WAS 950 PSIG WHEN THE LEAK WAS DETECTED. A NDT WAS NOT PERFORMED UNTIL A SAFE ENVIRONMENT FOR THE CONTRACTOR'S EMPLOYEES WAS ESTABLISHED. AN ADDITIONAL PRESSURE REDUCTION WAS MADE AND THE AREA AROUND THE LEAK WAS RE-EVALUATED. THEREAFTER, A DECISION WAS MADE TO ISOLATE THE LINE IN ORDER TO FURTHER ADDRESS THE IDENTIFIED LEAK LOCATION. THE LINE WAS PURGED AND ISOLATED. COURTESY NOTIFICATIONS WERE MADE TO LOCAL AUTHORITIES AND THE NEAR-BY RESIDENCE ABOUT THE ONGOING ACTIVITY AND THE NOISE ASSOCIATED WITH THE REQUIRED BLOWDOWN. THE NEIGHBOR DECLINED THE OFFER TO MOVE TO A LODGING ACCOMMODATION AND ELECTED TO VISIT A NEAR-BY RELATIVE. AFTER MIDNIGHT, THE LINE WAS ISOLATED. ON JANUARY 6, 2013, THE AREA OF INTEREST WAS TESTED BY THE NDT TEAM AFTER SECURING THE AREA TO BE SAFE TO OPERATE. PRELIMINARY NDT FINDINGS INDICATED THREE TRANSVERSE CRACKS; CIRCUMFERENTIALLY AT THE 09:00, 11:30 AND 12:00 O'CLOCK POSITIONS. THOSE FINDINGS INDICATED THE NEED TO FURTHER INVESTIGATE THE CRACKS FOR DEPTH AND WELD CONDITION OF THE WEST STOPPLE FITTING. THE NEED TO NDT THE SURFACE OF THE REMAINING WELDS OF THE WEST FITTING AS WELL AS THE EAST FITTING WAS DISCUSSED AND ACTED UPON. A CRACK IN A CIRCUMFERENTIAL WELD ON THE EAST STOPPLE FITTING WAS DISCOVERED AT THE 3 O'CLOCK POSITION. THE INSTALLED STOPPLE FITTINGS WITH THE ASSOCIATED WELDS WERE CUT OUT AND REMOVED. A REPLACEMENT OF THE CUT OUT SECTION OF THE PIPE WAS COMPLETED WITH A PRE-TESTED 30-IN PIPING. THIS REPAIR METHOD WAS DETERMINED TO BE THE APPROPRIATE PERMANENT REPAIR. A FOLLOW-UP REVIEW WITH THE HELP OF AN OUTSIDE CONSULTANT WAS UNDERTAKEN. ON DECEMBER 7, 2013, NDT WAS PERFORMED ON THE NEW WELDS AND THE ISOLATED SECTION WAS PURGED WITH A LEAK SURVEY PERFORMED IN AND AROUND THE EXCAVATED AREA. THE LINE WAS LOADED INCREMENTALLY AND RESURVEYED FOR ANY LEVELS OF LEL.