MONTANA - DAKOTA UTILITIES CO

Incident Narrative

ON JANUARY 18, 2023, MDU RESPONDED TO A STRUCTURE FIRE/EXPLOSION AT 4616 CORTEZ CIRCLE IN MANDAN, ND. AN UNINTENTIONAL RELEASE AND IGNITION OF NATURAL GAS OCCURRED. MDU PERSONNEL SECURED THE RELEASE BY SQUEEZING OFF THE SERVICE LINE. ON JANUARY 19, 2023, THE MANDAN FIRE DEPARTMENT AND ATF CONDUCTED AN INVESTIGATION AT 4616 CORTEZ CIRCLE IN MANDAN, ND, WITH REPRESENTATIVES FROM MDU AND THE ND PSC PRESENT. DURING EXAMINATION OF THE STRUCTURE'S INTERIOR, APPROXIMATELY TEN (10) FEET DOWNSTREAM OF THE GAS METER, THE NON-JURISDICTIONAL GAS PIPING WAS FOUND TO BE SEPARATED AT A CONNECTION POINT. A NATURAL GAS RANGE AND NATURAL GAS FURNACE WERE THE ONLY TWO FUEL FIRED APPLIANCES LOCATED IN THE STRUCTURE. THE CONNECTIONS AND PIPING TO THE RANGE AND FURNACE APPEARED TO BE INTACT. THE HEAT SOURCE OR CAUSE OF IGNITION WAS INCONCLUSIVE. FOLLOWING THE INVESTIGATION ON JANUARY 19, 2023, MDU MADE ATTEMPTS TO COORDINATE THE INVESTIGATION OF JURISDICTIONAL FACILITIES WITH ALL PARTIES. AFTER FAILED ATTEMPTS TO COORDINATE, THE COMPANY PROVIDED NOTIFICATION TO ALL PARTIES THAT AN INVESTIGATION WOULD COMMENCE ON AUGUST 15, 2023. MDU AND THE NORTH DAKOTA GAS PIPELINE SAFETY PROGRAM MANAGER/INSPECTOR CONDUCTED AN INVESTIGATION OF JURISDICTIONAL FACILITIES AT 4616 CORTEZ CIRCLE IN MANDAN, ND. A PRESSURE TEST WAS PERFORMED ON THE SERVICE LINE. THE PRESSURE TEST PASSED, HOLDING AT SYSTEM PRESSURE. ABOVE GROUND PIPING WAS INTACT UP TO THE RISER VALVE. THERE WAS A CRACKED NIPPLE BETWEEN THE RISER VALVE AND THE REGULATOR. THE ANALYSIS CONCLUDES THAT THE NIPPLE DAMAGE WAS DUE TO AN UNKNOWN OUTSIDE FORCE. IT IS UNKNOWN WHEN THE NIPPLE DAMAGE OCCURRED. MDU WAS ALLOWED TO INVESTIGATE JURISDICTIONAL FACILITIES ONLY. OCTOBER 11, 2023 - CORRECTED TIME IN FIELD A4. UPDATED FROM 12:26 TO 11:57.