ONEOK NGL PIPELINE, LLC

Incident Narrative

AT APPROXIMATELY 16:44 ON 7/26/2017, ONEOK FIELD REPRESENTATIVE WAS CONTACTED BY CARSTENSEN CONSTRUCTION AND INFORMED THE CONSTRUCTION CREW INTENDED TO BORE UNDER ONEOK'S BEAR CREEK LATERAL ALONG ST HWY 34 THE FOLLOWING DAY. THE LOCATION HAD BEEN PREVIOUSLY IDENTIFIED BY NORTH DAKOTA ONE-CALL TICKET NUMBER 17081108. ON 7/27/2017, ONEOK EMPLOYEE MET WITH CARSTENSEN CONSTRUCTION AT THE LOCATION TO PREPARE FOR THE BORE CROSSING. AT APPROXIMATELY 12:40, CARSTENSEN CONSTRUCTION CALIBRATED THEIR LOCATING INSTRUMENT WITH THE TRANSMITTER ON THE HEAD OF THE DRILL BORING TOOL. THE CALIBRATION OF THE EQUIPMENT WAS WITNESSED BY THE ONEOK EMPLOYEE. BEFORE STARTING THE BORE, CARSTENSEN CONSTRUCTION INFORMED THE ONEOK EMPLOYEE, THEY WERE GOING TO MOVE THE BORE ROUTE SOUTH, TOWARDS THE ROAD, BUT THIS WOULD NOT AFFECT THE CROSSING OF THE ONEOK PIPELINE. ONCE THE BORE BEGAN, CARSTENSEN CONSTRUCTION MONITORED THE DEPTH OF THE BORE HEAD EVERY 10 FEET AND SHARED THESE DEPTH READINGS WITH THE ONEOK EMPLOYEE. WHEN THE BORE WAS DIRECTLY UNDER THE ONEOK PIPELINE, CARSTENSEN CONSTRUCTION IDENTIFIED THE DEPTH OF THE BORE HEAD TO BE 15 FEET 8 INCHES, WHICH INDICATED THE BORE APPROXIMATELY 8 FEET 1 1/2 INCHES BELOW THE ONEOK PIPELINE. UPON COMPLETION OF THE INITIAL BORE AND THE DRILL HEAD EXITING THE GROUND DOWNSTREAM OF THE ONEOK PIPELINE, THE ONEOK EMPLOYEE LEFT THE DRILL SITE AT 15:17 HOURS. CARSTENSEN CONSTRUCTION CONTINUED TO WORK BY REAMING THE BORE IN THE OPPOSITE DIRECTION. AT APPROXIMATELY 18:07 ON THE 27TH, THE ONEOK EMPLOYEE RECEIVED A CALL FROM CARSTENSEN CONSTRUCTION STATING THE ONEOK PIPELINE HAD BEEN STRUCK AND A VAPOR CLOUD WAS VISIBLE AT THE BORE LOCATION. THE ONEOK REPRESENTATIVE IMMEDIATELY BEGAN THE EMERGENCY RESPONSE, CONTACTING ONEOK PIPELINE CONTROL CENTER AND HIS SUPERVISOR. THE ONEOK PIPELINE CONTROL CENTER CONFIRMED A PRESSURE DROP ON THE PIPELINE FROM 892 PSIG TO 650 PSIG AT WHICH TIME THE INJECTION FROM THE ONEOK ROCKIES MIDSTREAM BEAR CREEK PLANT WAS STOPPED AT 18:21. ONEOK PERSONNEL WERE DISPATCHED TO ISOLATE THE DAMAGED SECTION BY CLOSING THE UPSTREAM AND DOWNSTREAM BLOCK VALVES. APPROXIMATELY 9 MILES OF 8 INCH PIPELINE WAS ISOLATED. THE MCKENZIE COUNTY, NORTH DAKOTA, EMERGENCY MANAGER, COUNTY SHERRIFF'S DEPARTMENT AND THE WATFORD CITY FIRE DEPARTMENT WERE NOTIFIED AND ARRIVED ON SITE TO ASSIST AS NECESSARY. ST HWY 34 WAS CLOSED AT APPROXIMATELY 18:19 TO PREVENT TRAFFIC FROM ACCIDENTLY ACCESSING THE RELEASE SITE. A RESIDENT, LOCATED APPROXIMATELY 3000 FEET TO THE NORTH OF THE RELEASE, WAS ASKED TO SHELTER IN PLACE UNTIL SUCH TIME AS THE EXTENT OF THE RELEASE WAS DETERMINED. AT APPROXIMATELY 21:15 THE MCKENZIE COUNTY EMERGENCY MANAGER NOTIFIED ONEOK PERSONNEL THAT HE WAS GOING TO RELEASE THE EMERGENCY PERSONNEL AS HE BELIEVED ONEOK HAD SECURED THE SITE. ONEOK EMPLOYEES REMAINED ON SITE AT THE LOCATION AND CONTINUOUSLY MONITORED THE HYDROCARBON VAPORS UNTIL THE DAMAGE SECTION WAS REMOVED AND REPLACED ON JULY 30, 2017. ONCE ONEOK WAS ABLE TO EXCAVATE THE LOCATION AND IDENTIFY THE LOCATION OF THE RELEASE, IT WAS DETERMINED THE BORING STEM OF DRILL HEAD USED BY CARSTENSEN CONSTRUCTION HAD COME INTO CONTACT WITH THE BOTTOM OF THE ONEOK PIPELINE AND HAD WORN THROUGH THE WALL OF THE PIPE CAUSING THE RELEASE. UPON COMPLETION OF THE EXCAVATION, THE BOTTOM OF THE ONEOK PIPELINE WAS DETERMINED TO BE 7 FEET 6 1/2 INCHES BELOW THE SURFACE. THIS WAS THE SAME LOCATION THAT CARSTENSEN CONSTRUCTIONS TOOL HEAD LOCATOR HAD IDENTIFIED THE BORE HEAD TO BE AT A DEPTH OF 15 FEET 8 INCHES, WHICH SHOULD HAVE ALLOWED FOR ADEQUATE CLEARANCE FOR THE CROSSING. THE ISOLATED SECTION OF PIPE WAS PURGED OF HYDROCARBONS WITH NITROGEN AND THE DAMAGED SECTION REMOVED AND REPLACED WITH PRETESTED PIPE. THE UTILITY CROSSING WAS ALSO INSTALLED AT THIS TIME. THE BORING CONTRACTOR HAS ASSUMED LIABILITY FOR THE ACCIDENT. EDITED 5/17/2018 BY N. JONES