NORTHWESTERN CORPORATION

Incident Narrative

*UPDATE: AFTER FURTHER INSPECTION OF THE AREA WHERE THIS INCIDENT OCCURRED, IT WOULD BE APPROPRIATE TO CORRECT THE CLASS LOCATION FROM 1 TO A CLASS 3. ALSO, WITH FURTHER REVIEW OF THE ROOT CAUSE - NWE HAS CHANGED THE SELECTION TO ""ONE CALL NOTIFICATION PRACTICES NOT SUFFICIENT"". THE REASON THAT ""EXCAVATION PRACTICES NOT SUFFICIENT"" WAS ORIGINALLY SELECTED WAS DUE TO, IN ADDITION TO THE ONE CALL CENTER NOT BEING CONTACTED, THE CONTRACTOR WAS NOT TO BE DOING ANY WORK IN ANY CONTEXT AT THE LOCATION WHERE THE INCIDENT OCCURRED. THE WORK BEING DONE WAS COMPLETELY OUT OF THE SCOPE OF THE PROJECT AND NO WORK SHOULD HAVE BEEN BEING DONE WHEN THE LINE WAS HIT. THIS IS A RECLAMATION PROJECTED THAT IS BEING LED BY THE STATE OF MONTANA. ___________________________________________________________________________________________________ *NO CHANGE IN REPORT - SHOULD HAVE BEEN MARKED AS ""FINAL"" REPORT IN ORIGINAL REPORT - EVENT OCCURRED ON DECEMBER 7, 2018 NORTHWESTERN ENERGY ORIGINAL REPORT WAS MADE TO THE NRC ON DECEMBER 11, 2018. THIS IS THE DATE WHEN CONFIRMED DISCOVERY WAS MADE THAT THE LOSS OF NATURAL GAS EXCEEDED 3 MILLION CUBIC FEET. THE 48 HOUR UPDATE WAS MADE ON DECEMBER 13, 2018. TWO ADDITIONS WERE GIVEN IN THE 48 HOUR UPDATE: THE AMOUNT OF GAS LOST WAS INCORRECTLY REPORTED - CORRECT AMOUNT WAS 5,853 MCF (5,853,000 CUBIC FEET). THE OTHER UPDATE WAS TO INCLUDE THE CONTRACTOR INVOLVED IN THE INCIDENT - M.K. WEEDEN. THE NRC REPORT NUMBER FOR THIS UPDATE IS INCIDENT REPORT # 1232850. NO INJURIES, DEATHS, OR EVACUATIONS OCCURRED WITH THIS INCIDENT. NO LOCATE TICKET WAS SUBMITTED BY THE EXCAVATING PARTY WHEN THIS WORK WAS BEING DONE. 16:26 MST M.K. WEEDEN HIT A 12-INCH STEEL GAS MAIN LOCATED NEAR THE INTERSECTION OF FARRELL AND TEXAS AVE. WITH AN EXCAVATOR. THE LINE WAS AN INTERMEDIATE PRESSURE LINE OPERATING AT 50 PSIG. 16:45 MST NORTHWESTERN WAS NOTIFIED BY THE CONTRACTOR THAT A NWE GAS LINE WAS HIT NEAR THE INTERSECTION OF FARRELL AND TEXAS AVE. EMERGENCY RESPONSE WAS NOTIFIED AND NORTHWESTERN ENERGY PERSONNEL WAS DISPATCH TO EVALUATE THE HIT LINE FROM A SAFE DISTANCE. ADDITIONAL RESOURCES WERE CONTACTED TO ASSIST WITH THE ASSESSMENT OF DAMAGES AND TRAFFIC CONTROL. EMERGENCY RESPONSE PERSONNEL WAS ALSO ONSITE TO ASSIST. 17:00 MST NORTHWESTERN ENERGY WITH OTHER PERSONNEL CREATED A 360 DEGREE ZONE AROUND THE LOCATION OF THE HIT LINE AND WAS MONITORING THE GAS LEVELS TO CREATE A SAFE ZONE. CONTINUOUS AIR MONITORING WAS DONE UNTIL THE FLOW OF GAS WAS SHUT DOWN. 17:10 MST DUE TO THE SIZE OF THE LINE, NORTHWESTERN ENERGY NEEDED FURTHER ASSISTANCE BY OUR GAS TRANSMISSION DEPARTMENT WITH EQUIPMENT AND MATERIALS TO MAKE THE REPAIR. 17:30 MST MORE NWE PERSONNEL ARRIVED ON SITE AND FURTHER EVALUATION WAS CONDUCTED TO FINALIZE THE SAFEST AND BEST WAY TO CORRECT THE SITUATION. 03:45 MST THE FLOW OF GAS WAS SHUT DOWN BY INSERTING STOPPER. WITH FURTHER INVESTIGATION OF THE PIPE ONCE SAFE, IT WAS FOUND THAT THE DAMAGE BY THE EXCAVATOR BUCKET CREATED TWO PUNCTURES HOLES IN THE PIPE. ONE OF THE PUNCTURES WAS MEASURED AT 3 INCHES BY 2 INCHES. THE SECOND MEASURED AT 4 INCHES BY 3 INCHES. 8:15 MST REPAIRS WERE COMPLETED ON DECEMBER 8TH AND PIPE LINE WAS PLACED BACK IN SERVICE.