ENBRIDGE ENERGY, LIMITED PARTNERSHIP

Incident Narrative

ON APRIL 17, 2010 AT APPROXIMATELY 11:30 AM LOCAL TIME, WHILE PERFORMING INVESTIGATIVE FOLLOW-UP WORK AFTER A BRUSH FIRE CROSSED LINES 1 AND 2, ENBRIDGE ENVIRONMENTAL REPRESENTATIVE DISCOVERED AND REPORTED WHAT APPEARED TO BE A SMALL AMOUNT OF OIL ON THE RIGHT OF WAY AT MP 997.79. LINES 1 AND 2 WERE SHUT DOWN AS A PRECAUTION AND ENBRIDGE PIPELINE MAINTENANCE PERSONNEL WERE DISPATCHED TO INVESTIGATE. AFTER HAND-EXCAVATING THE IMPACTED AREA, A SMALL CRACK WAS DISCOVERED AND CONFIRMED ON THE LONGITUDINAL SEAM OF LINE 2 AT APPROXIMATELY 7:00 PM LOCAL TIME. THE DEFECT WAS LOCATED IN A MARSHY AREA AND THE SITE ACCESS AND INVESTIGATION PROGRESS WAS HAMPERED BY POOR SITE ACCESS AND GROUND CONDITIONS. EXTERNAL NOTIFICATIONS TO THE NATIONAL RESPONSE CENTER AND MINNESOTA STATE DUTY OFFICER WERE MADE UPON CONFIRMATION OF THE LEAK. NOTIFICATIONS WERE ALSO MADE DIRECTLY TO THE MINNESOTA OFFICE OF PIPELINE SAFETY, PHMSA, MINNESOTA POLLUTION CONTROL AGENCY AND THE MINNESOTA INTERAGENCY FIRE CENTER. ONCE THE PIPE WAS EXCAVATED THE ENTIRE LONG SEAM OF THE JOINT OF PIPE IN QUESTION WAS FIELD ASSESSED BY NDE (BOTH UT AND MAGNETIC PARTICLE INSPECTION). NO OTHER DEFECTS WERE IDENTIFIED. AN INTEGRITY ASSESSMENT WAS COMPLETED BY ENBRIDGE'S PIPELINE INTEGRITY GROUP AND THE PIPELINE WAS REPAIRED USING A PLIDCO SPLIT SLEEVE. THE RETURN TO SERVICE PLAN WAS REVIEWED WITH PHMSA AND MNOPS AND LINE 2 WAS RESTARTED ON APRIL 18 AT APPROXIMATELY 7:10 PM. THE INTEGRITY ASSESSMENT OF THIS LINE SEGMENT IS ONGOING AND THE SECTION OF PIPE IN QUESTION WILL BE CUT OUT FOR FURTHER METALLURGICAL ANALYSIS WHEN CONDITIONS ALLOW. ENBRIDGE ENVIRONMENT GROUP IS MANAGING SITE CLEANUP AND RESTORATION IN CONJUNCTION WITH A NUMBER OF AGENCIES (BOTH LOCAL AND STATE). A METALLURGICAL ANALYSIS WAS CONDUCTED AND THE LEAK WAS FOUND TO BE THE RESULT OF A HOOK CRACK THAT WAS FORMED AT THE TIME OF PIPE MANUFACTURE WHICH SUBSEQUENTLY EXTENDED BY FATIGUE THROUGH THE REMAINING THICKNESS OF THE PIPE. THERE WAS NO EVIDENCE THAT WAS FOUND TO SUGGEST THAT EITHER POST MANUFACTURING MECHANICAL DAMAGE OR CORROSION HAD CONTRIBUTED TO THE FLAW RESPONSIBLE FOR THE LEAK. THE AMOUNT OF CONTAMINATED SOIL REMOVED FROM THE LEAK SITE WAS 30 CUBIC YARDS.