TALLGRASS POWDER RIVER GATEWAY, LLC

Incident Narrative

5/12/2023 ORIGINAL NARRATIVE ON APRIL 13, 2023, OPERATOR PERSONNEL WERE OPENING VAULTS CONTAINING VALVES AHEAD OF BI-ANNUAL VALVE MAINTENANCE. WHEN THE VAULT FOR MOV-613 AT THE GUERNSEY NORTH TERMINAL WAS OPENED, CRUDE OIL WAS OBSERVED. THE FACILITY WAS IN A PAUSE BETWEEN BATCHES AND MOV-613 WAS ISOLATED TO CONTAIN THE LEAK. AFTER THE VAULT WAS CLEANED AND CLEARED FOR ENTRY, THE ANSI 150 FLANGE WAS FOUND TO HAVE FAILED AT THE AT THE 8:00 O'CLOCK POSITION ON DOWNSTREAM SIDE OF THE VALVE IN RELATION TO FLOW. NO DAMAGE WAS FOUND ON THE ISOLATION GASKET THAT WOULD INDICATE A FAILURE. AN INVESTIGATION IS STILL UNDERWAY TO DETERMINE APPARENT CAUSE AND A SUPPLEMENTAL REPORT WILL BE SUBMITTED ONCE THE INVESTIGATION IS COMPLETE. UNTIL TALLGRASS CONCLUDES ITS INVESTIGATION, IT HAS IMPLEMENTED CERTAIN INTERIM MEASURES INCLUDING OPENING THE VAULTS AT THE TERMINAL AND VISUALLY INSPECTING THEM WITH INCREASED FREQUENCY. THE CRUDE OIL RELEASE WAS CONFINED COMPLETELY TO THE VAULT CONTAINING MOV-613. THERE IS NO IMPACT TO THE TERMINAL OUTSIDE OF THE CONCRETE VAULT. ANOTHER VALVE IN THE TERMINAL, INSTALLED IN A SIMILAR FASHION AS MOV-613, WAS INSPECTED AS A PREVENTATIVE MEASURE. TALLGRASS WILL ALSO IMPLEMENT THE INTERIM MEASURES DISCUSSED ABOVE AT THE OTHER VALVE VAULT ON THE TERMINAL. 5/16/2024 UPDATE PART G APPARENT CAUSE UPDATED TO G7 INCORRECT OPERATION THE INVESTIGATION DETERMINED THAT THE FLANGE WAS NOT PROPERLY TORQUED WHICH RESULTED IN AN IMPROPER GASKET SEAL CAUSING PRODUCT TO BE RELEASED INTO THE FULLY CONTAINED CONCRETE VAULT. THE UNEVEN TORQUE PLACED UPON THE FLANGE CAUSED AN UNEVEN LOADING OF THE FLANGE FACE. ONCE THE FLANGE BOLTS WERE TIGHTENED TO 600 FT/LBS UTILISING A PROPER TORQUE SEQUENCE THE RELEASE TERMINATED. THE GASKET WAS REPLACED AT THE TIME OF THE EVENT. TALLGRASS HAS DEVELOPED SITE-SPECIFIC PROCEDURE TO INCLUDE PERIODIC INSPECTIONS OF THE VALVES IN VAULTS ON A WEEKLY BASIS.