HOLLY ENERGY PARTNERS - OPERATING, L.P.

Incident Narrative

A PRELIMINARY FINDING OF SUMP OVERFILLED WAS INITIALLY REPORTED TO NRC. AFTER FURTHER INVESTIGATION IT WAS DETERMINED THAT THE SUMP DID NOT OVERFILL BUT IN FACT FOUR CORNERS UNIT 2 CASE THERMAL RELIEF VALVE OPENED, FLOWING PRODUCT INTO THE SUMP DRAIN LINE. THE PRODUCT FLOWING INTO THE SUMP, ALERTED CONTROLLER WITH A SUMP ALARM, SIMULTANEOUSLY BACK FLOWED ONTO UNIT 2 SKID THROUGH THE PUMP SKID'S SUMP DRAIN LINE. THE BACK FLOW OF PRODUCT ONTO THE SKID WAS DETERMINED TO BE FROM THE UNIT 2 SKID SUMP DRAIN LINE CHECK VALVE BEING HELD OPEN BY DEBRIS. THIS ALLOWED PRODUCT TO BE RELEASED ON TO THE PUMP SKID AND APPROXIMATELY 15 GALLONS OF DIESEL ON THE GROUND. THE CASE THERMAL RELIEF VALVE WAS REPLACED. THE SUMP DRAIN LINE AND CHECK VALVE WERE CLEANED OF DEBRIS. PIPELINE WAS PUT BACK INTO NORMAL SERVICE. CORRECTIVE ACTIONS: BI MONTHLY PUMP STATION PREVENTATIVE MAINTENANCE CHECKS TO INCLUDE THE SUMP DRAIN LINES ARE FREE OF DEBRIS, AND THE SUMP DRAIN LINE CHECK VALVES ARE WORKING PROPERLY.