ANR PIPELINE CO

Incident Narrative

ON 26 NOVEMBER 2014 DURING A FLIGHT OVER THE GULF OF MEXICO, AN TRANSCANADA/ ANR PIPELINE COMPANY (ANR) TECHNICIAN OBSERVED A POTENTIAL LEAK NEAR TC OFFSHORE (TCO) ASSETS IN THE OUTER CONTINENTAL SHELF (OCS) EUGENE ISLAND BLOCK 55 (EI-55). THE LEAK WAS REPORTED TO ANR, OPERATOR FOR TC OFFSHORE, AS A BUBBLING PATTERN APPROXIMATELY TWO FEET IN DIAMETER OVER TC OFFSHORE'S 733 TRANSMISSION PIPELINE AT APPROXIMATE MILEPOST 40.8 (29.24206280, -91.50513440). FOLLOWING THE REPORT OF THE INCIDENT TO THE NATIONAL RESPONSE CENTER, TRANSCANADA/ANR MAINTAINED CONTACT AND UPDATED REGULARLY U.S. COAST GUARD, BSEE, AND PHMSA. WHILE PREPARING TO DISPATCH AN INVESTIGATION AND REPAIR VESSEL TO THE SITE, ANR SCHEDULED AERIAL PATROLS TWICE DAILY TO MONITOR THE LEAK. NO SHEEN OR PRODUCT WAS DOCUMENTED AT THE SITE FOR THE DURATION OF THE LEAK AND REPAIR. THE REPAIR VESSEL AND CONTRACT EMPLOYEES ARRIVED AT THE INCIDENT LOCATION ON 3 DECEMBER TO BEGIN EXPOSING THE PIPE FOR THE LEAK INVESTIGATION. COVER MATERIAL JETTING AND CONCRETE REMOVAL AT THE LEAK SITE WAS COMPLETED ON 8 DECEMBER. OBSERVATION AND INVESTIGATION BY THE DIVERS DETERMINED THAT THE LEAK WAS LOCATED AT THE TWELVE O'CLOCK POSITION IN THE LONGITUDINAL SEAM 45 INCHES DOWNSTREAM OF A GIRTH WELD. DURING THE COVER MATERIAL REMOVAL, ULTRASONIC TESTS TO DETERMINE THE POSSIBILITY OF METAL LOSS WERE CONDUCTED ON THE PIPELINE AT TWO LOCATIONS UPSTREAM AND DOWNSTREAM OF LEAK AREA. THESE TESTS INDICATED NO METAL LOSS TO THE PIPELINE. UPON DISCOVERY OF THE LEAK LOCATION, ANR DECIDED TO ISOLATE THE PIPELINE SEGMENT, REDUCE THE PRESSURE ON THE LINE, AND PERFORM ADDITIONAL TESTING AND ANALYSIS TO DETERMINE THE MOST EFFECTIVE REPAIR. ON 13 DECEMBER, SUBSEA VALVE 733-1A-2 LOCATED AT EUGENE ISLAND BLOCK 63 (EI-63) WAS CLOSED, ISOLATING THE 733 PIPELINE BETWEEN EI-63 AND ANR'S PATTERSON COMPRESSOR STATION LOCATED IN ST. MARY PARISH, LOUISIANA. ADDITIONALLY, THE PRODUCER, CASTEX, WAS SHUT-IN AND THE VALVE WAS CLOSED AT EUGENE ISLAND BLOCK 18. PRESSURE ON THE 733 LINE WAS REDUCED FROM APPROXIMATELY 800 PSIG TO 400 PSIG AND FLARED AT THE PATTERSON COMPRESSOR STATION. FOLLOWING THE REDUCTION IN PRESSURE, TIME OF FLIGHT DIFFRACTION NON-DESTRUCTIVE TESTING (NDT) WAS CONDUCTED ON 15 DECEMBER 2014 TO DETERMINE THE CHARACTERISTICS AND LOCATION OF LEAK. THE AREA INSPECTED INCLUDED ONE FOOT UPSTREAM AND ONE FOOT DOWNSTREAM OF THE ANOMALY AREA. TESTING INDICATED A SMALL DEFECT LOCATED WITHIN THE LONGITUDINAL SEAM WITH NO INDICATION OF CRACKS OR LACK OF FUSION. ON 18 DECEMBER AT 05:00 CST, A PLIDCO BOLT-ON CLAMP WAS SUCCESSFULLY INSTALLED OVER THE LEAK LOCATION BY QUALIFIED CONTRACT EMPLOYEES. THE CLAMP IS CONSIDERED A PERMANENT REPAIR. FOLLOWING THE INSTALLATION OF THE CLAMP, PIPELINE PRESSURE WAS INCREASED, THE PRODUCER VALVE AT EI-18 WAS ALLOWED TO RESUME FLOWING, AND THE SUBSEA VALVE AT EI-63 WILL BE REOPENED WHEN IT CAN BE SAFELY ACCESSED. THERE WERE NO INDICATIONS OF FURTHER LEAKAGE AT THE REPAIR LOCATION.