NORTHWESTERN CORPORATION

Incident Narrative

EVENTS ON FEB 6 2018 NORTHWESTERN ORIGINALLY REPORTED TO THE NRC WITH THE NOTIFICATION TIME OF 8:58. THIS WAS AN ERROR IN REPORTING. THE TIME NORTHWESTERN RECEIVED THE FIRST NOTIFICATION FROM 911 WAS 10:14 CST. THIS TIME WAS RETRIEVED FROM OUR INCOMING CALL LONG AND VERIFIED TO BE ACCURATE. THE INCORRECT TIME OF 8:58 INCORRECTLY REPORTED REPRESENTED THE DATE/TIME STAMP IN CUSTOMER INFORMATION SYSTEM AND IS IN MST TIME ZONE. THE INCIDENT LOCATION IS IN CST TIME ZONE. IN ADDITION THE DATE/TIME STAMP WAS INCORRECTLY ATTACHED TO TWO CONSECUTIVE ORDERS BY THE CUSTOMER SERVICE REPRESENTATIVE. 10:14 CST NORTHWESTERN RECEIVED A CALL FROM 911 REQUESTING ASSISTANCE AT 207 N 2ND IN ABERDEEN SD. HOUSE WAS A VACANT PREMISE WITH NO ONE OCCUPYING THE STRUCTURE. 10:23 CST NORTHWESTERN ARRIVED ON SITE. 10:28 CST POWER SHUT OFF TO PREMISE AT THE POLE. 10:50 CST ADJACENT STRUCTURES CHECKED WITH FIRE DEPARTMENT 10:55 CST FIRE DEPARTMENT REQUESTED SERVICE LINE TO BE SHUT OFF 11:20 CST SERVICE WAS SQUEEZED OFF APPROXIMATELY 40 FT. FROM HOME DUE TO FIRE. 11:28 TO 12:00 CST SD PUC NOTIFIED. ODORMETER, LEAK SURVEY AND ADDITIONAL BAR HOLING COMPLETED. NO EVIDENCE OF ADDITIONAL GAS ISSUES FOUND. 12:00 TO 17:00 CST AREA MONITORED AND TECHNICIANS ON SITE TO ASSIST FIRE DEPARTMENT AS NEEDED. 13:25 CST NRC NOTIFIED. DUE TO HEAVY GROUND FROST A THAW BLANKET WAS APPLIED TO BE USE TO THAW THE GROUND TO COMPLETE THE FULL RETIREMENT OF THE SERVICE ON FEB 12 2018. FEB 7 2018 PREMISE HISTORICALLY A RENTAL HOME WITH NO OCCUPANTS AT THIS TIME. LAST KNOWN OCCUPANTS INTERVIEWED BY FIRE MARSHALL AND NORTHWESTERN REPRESENTATIVE. OCCUPANTS INDICATED NO NOTICEABLE GAS SMELL INSIDE THE HOME. OCCUPANTS' WASHER AND DRYER LOCATED IN THE BASEMENT ON THE WALL DIRECTLY ASSOCIATED WITH NATURAL GAS METER. OCCUPANTS DESCRIBED AN ISSUE WITH THE BASEMENT WALL CRACKING DUE TO WALL MOVEMENT AND CREATING A DRAFT IN THE HOME. LANDLORD SUPPLIED CAULKING TO OCCUPANTS TO FILL IN CRACKS CREATED BY BASEMENT WALL MOVEMENT. METER RETRIEVED AND OBTAINED BY NORTHWESTERN. PER FIRE MARSHALL REQUEST PRESSURE TEST ATTEMPTED FROM SQUEEZE POINT TO METER AND FAILED. SITE RELEASED BY FIRE MARSHALL TO HOME OWNER INSURANCE. FEB 9 2018 ATTEMPTED TO RETIRE SERVICE FROM SQUEEZE OFF POINT THE MAIN IN ALLEY AS THAW BLANKET HAD BEEN ON SINCE FEB 6 2018. INSUFFICIENT THAW. THAW BLANKET PUT BACK ON MAIN/SERVICE AREA. FEB 12 2018 SUFFICIENT THAW. SERVICE RETIRED AT THE MAIN. FEB 21 2018 COORDINATED INVESTIGATION WITH ALL CONCERNED PARTIES INCLUDING THE SD PUC TO DIG UP SERVICE PIPE FROM SQUEEZE OFF POINT TO METER. THAW BLANKETS PUT ON SERVICE THE WEEK PRIOR. EXCAVATED PARTIAL AREA. DUE TO UNFORESEEN CONCRETE PATIO INSUFFICIENT THAW AROUND METER AREA. REAPPLIED THE THAW BLANKET. FEB 23 2018 COORDINATED INVESTIGATION WITH ALL CONCERNED PARTIES INCLUDING THE SD PUC TO RESUME EXCAVATION. SERVICE AND RISER AREA FULLY EXCAVATED. FRACTURE FOUND AT THE RISER CONNECTION TO A 90 DEGREE ELBOW. DAMAGED RISER AND ELBOW REMOVED FROM THE GROUND. PRESSURE TEST FROM PIPE REMOVAL ELBOW TO SQUEEZE OFF POINT SUCCESSFUL. NO FURTHER DAMAGE. DUE TO THE FRACTURED SURFACE OF THE ELBOW AND PIPE, NORTHWESTERN AND OUTSIDE INVESTIGATION RETAINED BY NORTHWESTERN BELIEVE THE EVIDENCE SUPPORTS THE FRACTURE TO BE CAUSE BY AN OUTSIDE FORCE, LIKELY THE BASEMENT WALL MOVEMENT, CREATED THE FORCE ON THE PIPE TO CAUSE THE FRACTURE.