NUSTAR PIPELINE OPERATING PARTNERSHIP L.P.

Incident Narrative

AROUND 6:30 PM, 2/4/2024, A LANDOWNER NEAR THE WOOD RIVER 6-INCH LATERAL IN ST. CHARLES COUNTY, MO, WAS PICKING UP A SCENT OF AMMONIA, SO HE NOTIFIED AUTHORITIES, WHO NOTIFIED NUSTAR. THE LATERAL WAS NOT RUNNING AT THE TIME OF THE LEAK, BUT THE EAST LEG WAS SHUT DOWN AND BLOCKED IN AT O'FALLON PUMP STATION. NUSTAR CONFIRMED THE LEAK AT 8:08 PM. ANHYDROUS AMMONIA WAS DISCOVERED BUBBLING UP FROM THE GROUND, CAUSING VAPORS APPROXIMATELY 12 INCHES OFF THE GROUND AND TRAVELING 6-8 FEET LATERALLY BEFORE DISSIPATING AS THE PRESSURE DIMINISHED. THE 6-INCH LATERAL WAS ISOLATED BY CLOSING VALVES 12-1, AND THE WOOD RIVER DELIVERY WAS OPENED, REDUCING THE PRESSURE TO APPROXIMATELY 154 PSI. VALVE 12-2 WAS CLOSED TO ISOLATE THE LEAKING SEGMENT FURTHER. THE AMMONIA BUBBLING AND VAPORS REDUCED SIGNIFICANTLY AFTER VALVE CLOSURE. A SLIGHT SMELL WAS DETECTED (OFF AND ON) ABOUT 0.3 MILES AWAY AT THE LANDOWNERS HOUSE. NO EVACUATIONS OR ROAD CLOSURES WERE NECESSARY. IT WAS DETERMINED TO BE A SMALL ENOUGH LEAK THAT WE DID NOT SET UP AN OFFICIAL INCIDENT COMMAND CENTER. HSE COMPLETED ICS FORMS TO DOCUMENT THE RESPONSE. AN EMPLOYEE REMAINED ON SITE OVERNIGHT TO MONITOR THE AREA. ALL NOTIFICATIONS WERE MADE. THE RELEASE QUANTITY WAS INITIALLY REPORTED AT 200 POUNDS. AFTER PRELIMINARY ENGINEERING CALCULATIONS WERE COMPLETED, THE LEAK VOLUME WAS ESTIMATED TO BE 1000 POUNDS. THE ESTIMATED VOLUME WAS REPORTED ON THE 48-HOUR UPDATE CALL TO NRC. THE MAINTENANCE CREWS ARRIVED ON-SITE ON THE MORNING OF 2/5/2024. THEY BEGAN EXCAVATING THE PIPELINE UPSTREAM OF THE LEAK TO WELD ON A STOPPLE TEE. UPON COMPLETION, THEY EXCAVATED THE LEAK AREA TO DETERMINE HOW MUCH PIPE NEEDED TO BE REPLACED. A CLAMP WAS INSTALLED TO STOP THE LEAK AT 4:35 PM ON 2/5/2024. ON 2/6/2024, THE EXCAVATION WAS COMPLETED DOWNSTREAM FOR A SECOND STOPPLE TEE INSTALLATION. STOPPLES WERE INSTALLED UPSTREAM AND DOWNSTREAM OF THE LEAK LOCATION TO CUT OUT THE DAMAGED LINE SAFELY. THE LINE WAS CUT OUT AND REPLACED WITH PRE-TESTED PIPE. THE LATERAL VALVE WAS REOPENED TO FILL THE LINE ON 2/8/2024 AT 8:29 AM. MO-DNR APPROVED THE AMMONIA-ENRICHED SOIL TO BE HAULED TO THE J-1 PUMP STATION AND LAND-FARMED. THE CUTOUT SECTION OF THE PIPE WAS SENT FOR METALLURGICAL ANALYSIS TO DETERMINE THE CAUSE OF THE PINHOLE. RESULTS OF METALLURGICAL ANALYSIS: THE PINHOLE FAILURE WAS DUE TO A MANUFACTURING/WELDING DEFECT AT THE WELD SEAM. A LOCALIZED INCLUSION OF COPPER WAS PRESENT IN THE WELD SEAM THAT CAUSED GALVANIC CORROSION TO OCCUR AND CREATE A PINHOLE LEAK. THE COPPER HAD A GALVANIC EFFECT WITH THE IRON IN THE CARBON STEEL. THE COPPER ACTED AS THE CATHODE WHILE THE IRON ACTED AS AN ANODE. THE CARBON STEEL PREFERENTIALLY CORRODED.