NUSTAR PIPELINE OPERATING PARTNERSHIP L.P.

Incident Narrative

ON 11/27/10 AT 15:00 A LOCAL LANDOWNER NOTIFIED NUSTAR CONTROL CENTER REGARDING AN AMMONIA ODOR NEAR VALVE 6-16. THE PIPELINE WAS SHUTDOWN AT 15:15. ON 11/27/10 AT 17:00 A NUSTAR TECHNICIAN ARRIVED ON-SITE AND CONFIRMED THAT AN AMMONIA ODOR WAS PRESENT. ON 11/28/10 AT 14:30 NUSTAR RESOURCES ARRIVED ON-SITE TO BEGIN EXCAVATION OF THE STOPPLE TEE. ON 11/28/10 AT 17:55 NUSTAR UNCOVERED THE LEAK SITE AND BASED ON VISUAL OBSERVATION DETERMINED THE LEAK WOULD EXCEED THE REPORTABLE QUANTITY. AT 18:31 ON 11/28/10, NUSTAR CONTACTED THE NRC TO MAKE NOTIFICATION OF A REPORTABLE LEAK INCIDENT. ANHYDROUS AMMONIA WAS LEAKING FROM A HORIZONTAL WELD ON THE SIDE OF THE STOPPLE TEE. THE STOPPLE TEE WAS REPLACED. THE LEAKING STOPPLE TEE HAS BEEN SENT FOR METALLURGICAL ANALYSIS TO DETERMINE CAUSE OF THE INCIDENT. THE LEAK OCCURRED IN THE LONGITUDINAL WELD OF THE STOPPLE FITTING. THE TWO HALVES OF THE FITTING WERE POORLY FITTED TOGETHER WHICH PROBABLY HINDERED AN ADEQUATE ROOT PASS. THE LACK OF AN ADEQUATE ROOT PASS ALLOWED FOR A CRACK-LIKE CONDITION ON THE INSIDE SURFACE OF THE WELD. THE CRACK PROPAGATED THROUGH THE WELD DUE TO PRESSURE-CYCLE FATIGUE WHICH WAS POSSIBLY ACCELERATED BY BENDING STRESSES CAUSED BY THE POOR FIT-UP.