NUSTAR PIPELINE OPERATING PARTNERSHIP L.P.

Incident Narrative

AT APPROXIMATELY 19:00 ON 5/6/13, THE ST. CHARLES COUNTY FIRE ASSOCIATION CALLED THE NUSTAR CONTROL CENTER WITH A COMPLAINT OF AMMONIA SMELL NEAR A FARM RESIDENCE. THE PIPELINE WAS SHUT DOWN AT THIS TIME. NOTE: THE FORM WILL NOT ALLOW A DATE PREVIOUS TO THE ACCIDENT DATE AND TIME. A NUSTAR EMPLOYEE ARRIVED ON SITE AT APPROXIMATELY 20:20 AND CONFIRMED THE AMMONIA SMELL. NUSTAR RESOURCES WERE MOBILIZED TO THE SITE AT APPROXIMATELY 07:00 ON 5/7. EXCAVATION UNCOVERED A LEAKING STOPPLE TEE AT 09:55 ON 5/7. THE LEAK WAS COMING FROM THE HORIZONTAL WELD ON A STOPPLE TEE. A REPORTABLE QUANTITY WAS DETERMINED AT 10:50 ON 5/7 AND THE NRC, STATE EMERGENCY MANAGEMENT, AND LOCAL LEPC WERE GIVEN TELEPHONE NOTIFICATION. THE STOPPLE TEE WAS CUT OUT, A PUP JOINT INSTALLED AND THE LINE WAS RETURNED TO SERVICE AT 10:50 ON 5/9/13. THE REMOVED STOPPLE TEE HAS BEEN SENT TO A METALLURGIST FOR ANALYSIS. SUPPLEMENTAL INFORMATION: THE PIPE DIAMETER IS 8 INCH. APPROXIMATELY 90 CUBIC YARDS OF SOIL WAS REMOVED. METALLURGICAL SUMMARY AND CONCLUSION: THE LEAK WAS CAUSED BY A FATIGUE CRACK THAT DEVELOPED IN THE LONGITUDINAL SEAM WELD OF THE STOPPLE FITTING. THE CRACK INITIATED AT AN AREA OF MISALIGNMENT OF THE CUFF EDGES AND INADEQUATE WELD PENETRATION; A FABRICATION DEFECT CREATED WHEN THE FITTING WAS INSTALLED ON THE PIPELINE. THE INCOMPLETE ROOT PASS CREATED A NOTCH-LIKE STRESS CONCENTRATION WHICH ALLOWED FOR THE INITIATION OF A CRACK. THE CRACK PROPAGATED BY FATIGUE FROM OPERATING PRESSURE FLUCTUATIONS UNTIL IT WAS NEARLY THROUGH THE WELD. THE REMAINING INTACT LIGAMENT WAS UNABLE TO CONTAIN THE INTERNAL LINE PRESSURE. *UPDATE 10-7-15 - MODIFIED SECTION A. 18B - RESOURCES ARRIVED ON-SITE.