DAKOTA GASIFICATION COMPANY

Incident Narrative

DGC BECAME AWARE OF LOG ENTRY THAT STATED H2S LEVELS AT THE TIOGA STATION. REVIEWED THE CURRENT STATUS OF THE TIOGA STATION ON PROCESS EXPLORER AND NOTED THAT BOTH FIXED H2S MONITORS NEAR GA7411 WERE PEGGED OUT AT 100 PPM. VIEWED LIVE CAMERA IMAGERY VIA ARLO CAMERA FACING THE PUMP, COULD VISUALLY SEE A LEAK COMING FROM GA7411 SEAL AREA. DISPATCHED A PIPELINE OPS CREW AND PROTECTION SERVICES TECHNICIAN TO THE SITE TO OBSERVE AND AIR MONITOR THE AREA. NO H2S WAS DETECTED OUTSIDE THE TIOGA PUMP HOUSE. PIPELINE OPS CHECKED ISOLATION VALVES AND ADDED VALVE SEALANT TO BOTH VALVES. STARTED THE FLARE AND ATTEMPTED TO DE-PRESSURE THE SEAL SYSTEM TO THE FLARE. SEVERAL ATTEMPTS OF GOING TO THE FLARE WERE UNSUCCESSFUL, THIS INDICATING A TOTAL SEAL FAILURE. THE BUILDING WAS VENTILATED OF H2S TO A LEVEL BELOW 1 PPM. PIPELINE OPS LEFT FOR THE EVENING; THE BUILDING WAS CLOSED UP TO PREVENT H2S FROM LEAVING THE SITE. PROTECTION SERVICES TECH MONITORED THE AREA OUTSIDE OF THE STATION AND DOWN THE ROAD TO KEEP PEOPLE AWAY FROM THE SITE UNTIL RELIEVED AT 7 AM BY PIPELINE OPS STAFF THE NEXT MORNING. THE PUMP WAS BLINDED FROM THE PROCESS AND FLUSHED WITH DIESEL FUEL TO REMOVE THE REMAINING PRODUCT. DGC HAS NOT YET SCHEDULED CORRECTIVE MAINTENANCE ACTIVITIES ON THE SEAL SYSTEM TO UNDERSTAND THE CAUSE OF FAILURE AT THIS TIME. ADDITIONALLY, DGC IS ATTEMPTING TO QUANTIFY THE RELEASED VOLUME OF CARBON DIOXIDE. THE REPORTED QUANTITY IS NOT THE ANTICIPATED FINAL VOLUME.