ENBRIDGE STORAGE (CUSHING) L.L.C.

Incident Narrative

ON NOVEMBER 4, 2020 AT APPROXIMATELY 12:32 PM CT DURING A ROUTINE ANNUAL TANK INSPECTION, OIL WAS DISCOVERED ON THE INTERNAL ROOF OF TANK 3012 AT THE CUSHING TERMINAL. APPROXIMATELY 5 BARRELS OF OIL WAS DISCOVERED IN THE BULKHEADS ON THE INTERNAL FLOATING ROOF. GIVEN THAT THE OIL WAS CONTAINED BETWEEN THE FLOATING ROOF AND THE FIXED ROOF, AN ACTION PLAN WAS DEVELOPED TO TAKE THE TANK OUT OF SERVICE TO REMOVE THE OIL. ON DECEMBER 7, 2020 IT WAS DETERMINED THAT A FAILURE OCCURRED DUE TO INCORRECT OPERATION AFTER AN INVESTIGATION FOUND THAT THE TANKS INTERNAL FLOATING ROOF WAS SET DOWN ON ITS LEGS MULTIPLE TIMES SINCE THE LAST OUT OF SERVICE INSPECTION IN FEBRUARY OF 2014. FURTHER INVESTIGATION FOUND THAT THE LEG HEIGHT SET WITHIN THE SCADA SYSTEM DIDN'T MATCH THE LEG HEIGHT ON THE FLOATING ROOF IN THE FIELD WHICH WAS LEFT IN THE HIGH (MAINTENANCE) POSITION AFTER THE LAST INTERNAL INSPECTION. ENBRIDGE'S PROCEDURES REQUIRE THAT THE LEGS BE RETURNED TO OPERATIONAL (LOW LEG) POSITION. DRAWING OIL DOWN AT OPERATIONAL FLOW RATES WHILE THE ROOF WAS ON ITS LEGS CAUSED AIR TO BE SUCKED AROUND THE ROOF SEAL TO FORM A VAPOR SPACE UNDER THE ROOF. WHEN THE TANK WAS THEN FILLED AT OPERATIONAL FILL RATES IT CAUSED AIR TO VENT THROUGH APPURTENANCES AS THE ROOF VENT IS NOT DESIGNED FOR FULL FLOW RATE. OVER MANY FILL AND WITHDRAW CYCLES THIS CAUSED OIL TO SPRAY ONTO THE TOP SIDE OF THE FLOATING ROOF TO RAISE CONCERN AND INVESTIGATE. ALL CRUDE HAS BEEN CLEANED UP AND THE TANK REMAINS OUT OF SERVICE FOR ITS ANNUAL API 653 TANK INSPECTION.