MONTANA - DAKOTA UTILITIES CO

Incident Narrative

AT 16:45 ON 3/20/2019 LOCAL MANAGEMENT WAS INFORMED BY EMERGENCY RESPONDERS THAT A POSSIBLE EXPLOSION HAD OCCURRED AT 718 RIVER RD, GLENDIVE, MT. TECHNICIANS WERE DISPATCHED IMMEDIATELY AFTER NOTIFICATION AND UPON ARRIVAL TECHNICIANS BEGAN TO MAKE THE SCENE SAFE. THE TECHNICIANS CONFIRMED THAT AN EXPLOSION HAD OCCURRED AT A PRIVATE RESIDENCE RESULTING IN BURN INJURIES TO A RESIDENT. GAS METER TO THE HOME WAS SHUT OFF. A COMBUSTIBLE GAS INDICATOR WAS USED INSIDE THE HOME, DETECTING A PRESENCE OF NATURAL GAS. THE INVESTIGATION CONTINUED OUTSIDE WITH THE PRESENCE OF GAS BEING FOUND IN SOIL. DURING THIS INVESTIGATION A LEAK WAS DETECTED ON A MECHANICAL NUT FOLLOWER COUPLING ON THE 2IN STEEL MAIN WHICH WAS SECURED AT 04:48 3/21/2019. FOLLOW UP INVESTIGATION PROVED NO INDICATION OF LEAKS ON THE JURISDICTIONAL SERVICE LINE. ADDITIONALLY, TESTING OF CUSTOMER OWNED FACILITIES PROVIDED NO INDICATION OF MATERIAL LEAKS. THE MAIN HAD BEEN INSTALLED IN 1962. NO INDICATIONS OF A LEAK WERE FOUND IN THE PRIOR TWO LEAK SURVEYS, CONDUCTED IN 2014 AND 2018, RESPECTIVELY. IN THE ABSENCE OF ANOTHER IDENTIFIABLE SOURCE, THE LEAKING MECHANICAL FITTING ON THE MAIN MAY HAVE BEEN A SOURCE OF FUEL FOR THE EXPLOSION THAT OCCURRED. HOWEVER, AN IDENTIFIED PATH OF MIGRATION HAS NOT BEEN DETERMINED FOR THE SOURCE OF FUEL TO ENTER THE HOME. EXTREME WINTER TEMPERATURE AND FROST CONDITIONS AT THE MECHANICAL FITTING MAY HAVE AFFECTED SOIL CONDITIONS SURROUNDING THE FITTING ALONG WITH POTENTIAL FOR ABNORMAL CONTRACTION/EXPANSION OF THE FITTING AND PIPE COMPONENTS. A REQUIRED FOLLOW UP REPORT #1240787 WAS SUBMITTED AS THE 48 HOUR FOLLOW UP REPORT.