ENBRIDGE ENERGY, LIMITED PARTNERSHIP

Incident Narrative

DURING PIGGING OPERATIONS AT THE DEER RIVER STATION ON APRIL 22, 2024, AT APPROXIMATELY 11:17 PM CDT, THE EDMONTON CONTROL CENTER RECEIVED A GAS ALARM IN THE LINE 4 PUMP HOUSE. SIMULTANEOUSLY, OPERATIONS TECHNICIANS ON SITE HEARD LINE 4 PUMPING EQUIPMENT SHUT DOWN AND WENT TO INVESTIGATE. WARNING BEACONS WERE FOUND TO BE ACTIVE OUTSIDE OF THE PUMP HOUSE AND CRUDE OIL WAS DISCOVERED ON THE CONCRETE FLOOR. OPERATIONS CONFIRMED WITH THE CONTROL CENTER THAT THERE WAS AN ACTIVE RELEASE, AND THE STATION WAS ISOLATED. THE SOURCE OF THE RELEASE WAS IDENTIFIED AS AN INBOARD AND OUTBOARD SEAL FAILURE ON UNIT 3. ADDITIONAL RESOURCES ARRIVED ON SITE FOR CLEANUP AND REPAIRS. APPROXIMATELY 125 GALLONS OF CRUDE OIL WAS RELEASED WITH THE MAJORITY GOING TO THE STATION SUMP. CLEANUP WAS COMPLETED AND MATERIALS WERE DISPOSED OF VIA THIRD-PARTY CONTRACTOR. THE SEALS WERE REPLACED, AND UNIT 3 WAS RETURNED TO SERVICE. THE CAUSE OF THE RELEASE WAS FROM A TRANSIENT WAVE FROM UNIT 2 INTO UNIT 3 DUE TO LOW STATION SUCTION PRESSURE. THIS LOW PRESSURE WAS A RESULT OF PIG 1 BEING CAUGHT IN THE TRAP RECEIVING LINE TEE, CREATING A LARGE DIFFERENTIAL PRESSURE ACROSS PIG 1. WHEN PIG 2 WAS LANDED, IT PUSHED PIG 1 FORWARD RELIEVING THE PRESSURE OBSTRUCTION. THE NEAR-INSTANT STATION SUCTION PRESSURE INCREASE CAUSED UNIT 2 AND UNIT 3 TO DEADHEAD AGAINST A PARTIALLY CLOSED PRESSURE CONTROL VALVE WHICH CAUSED THE SEALS ON UNIT 3 TO FAIL.