ONEOK NGL PIPELINE, LLC

Incident Narrative

3/10/2015 CREWS WERE LOCATED AT PRAIRIE VIEW JCT. TO INSTALL A TAPPING TEE ON EXISTING STATION PIPE. PRIOR TO WELDING THE TEE, FOUR AND SIX INCHES OF SOIL HAD BEEN REMOVED FROM AROUND THE PIPE RISER AND EXISTING COATING WAS REMOVED. A TORCH WAS USED TO REMOVE THE RESIDUAL COATING PRIOR TO FITTING THE TEE TO THE PIPE. A SMALL FIRE, APPROXIMATELY ONE TO TWO INCHES TALL, IGNITED ON THE GROUND AND WAS QUICKLY EXTINGUISHED BY THE WORKERS GLOVES. GAS MONITORING HAD NOT AND DID NOT DETECT HYDROCARBONS, NO LEAK SOURCE WAS APPARENT; THEREFORE THE FUEL SOURCE WAS NOT BELIEVED TO BE PIPELINE RELATED. ON 3/13/2015, THE CONTRACTOR BEGAN FURTHER EXCAVATION AROUND THE RISER AND DISCOVERED TRACES OF WHAT WAS BELIEVED TO BE HYDROCARBON VAPOR IN THE EXCAVATION BETWEEN 1 FT. AND 2 FT. DEEP. ONEOK THAN BEGAN TO LOOK FOR A SOURCE OF THE HYDROCARBON. CONCENTRATION OF HYDROCARBON VAPOR WAS LOCATED DIRECTLY OVER 6' STATION PIPING BETWEEN THE MADILL PIG RECEIVER AND THE STERLING 1 PIPELINE. AT THIS TIME IT WAS SUSPECTED THIS STATION PIPE TO BE THE SOURCE AND THE DECISION WAS MADE TO REMOVE THE LINE. DUE TO THE DEPTH OF PIPE AND LIMITED SPACE OF THE SITE, THE 6' STATION PIPE WAS CUT IN HALF AND REMOVED IN ORDER TO VISUALLY INSPECT THE PIPE (COMPLETED ON 3/16). UPON VISUAL INSPECTION OF THE PIPE AFTER REMOVAL, A LEAK SOURCE WAS NOT APPARENT. NEW PIPE WAS INSTALLED ON 3/13 @ 20:00. ONEOK THAN BEGAN FURTHER ACTIONS TO IDENTIFY THE SOURCE OF THE HYDROCARBONS. 3 ACTIVITIES WERE UNDERTAKEN: 1) EXCAVATION OF STOPPLE TEES, TIE-IN WELDS, FITTINGS, AND NEW PIPING INSTALLED ON STERLING PIPELINES DURING THE CONSTRUCTION OF PRAIRIE VIEW SITE IN THE FIRST HALF OF 2014, 2) THE SHUT DOWN AND PRESSURE MONITORING OF PIPELINES ASSOCIATED WITH THE SITE, STERLING 1, STERLING 2 AND MADILL LATERAL, AND 3) HYDROTESTING OF THE REMOVED SECTION OF PIPE. #1: ALL PIPELINE DITCHES ENTERING PRAIRIE VIEW JUNCTION WERE EVALUATED FOR ANY PRODUCT THAT MAY HAVE MIGRATED INTO THE SITE FROM AN OUTSIDE SOURCE. THROUGHOUT ALL EXCAVATION, HYDROCARBON VAPORS WERE ONLY PRESENT IN THE ONE TO TWO FOOT DEPTH RANGE. ONEOK PIPING IS LOCATED AT A DEPTH GREATER THAN 3 FEET. #2: THE MADILL PLANT SHUT DOWN ON 3/18 @ 16:30 AND THE PRESSURES WERE MONITORED FOR 16 HOURS ON AN ISOLATED SECTION OF THE MADILL LATERAL, INCLUDING PRAIRIE VIEW JUNCTION PIPING. AFTER REVIEWING THE DATA, IT WAS DETERMINED NO LEAKS WERE PRESENT. STERLING PIPELINES SHUT DOWN AND ISOLATED ON 3/19 @ 14:30 AND 15:45 RESPECTIVELY UTILIZING UPSTREAM AND DOWNSTREAM VALVES OF PRAIRIE VIEW STATION IN ADDITION TO THE ISOLATION VALVES AT PRAIRIE VIEW JUNCTION ITSELF (4 ISOLATED SECTIONS). THE PRESSURES WERE MONITORED AND RECORDED EVERY 15 MINUTES UNTIL 3/20 @ 14:00 FOR STERLING 1 AND 3/20 @ 18:00 FOR STERLING 2. A REVIEW OF THE DATA WAS COMPLETED AND DETERMINED NO LEAKS WERE PRESENT ON STERLING 1 OR STERLING 2 BY OPERATIONS PERSONNEL AND COMPANY ENGINEERS. STERLING 1 & 2 WERE SUBSEQUENTLY RETURNED TO NORMAL OPERATION. STERLING 3 WAS NOT IDENTIFIED AS A SOURCE DUE TO THE CHARACTERISTICS OF THE HYDROCARBON OBSERVED AS WELL AS WHERE THE HYDROCARBONS WERE OBSERVED IN THE STATION. #3: THE REMOVED 6' STATION PIPING WAS HYDROTESTED ON MARCH 18TH, AND NO LEAKS DISCOVERED. DURING THE INVESTIGATION, IT WAS BROUGHT TO ONEOK'S ATTENTION FROM OUR LOCAL OPERATOR THAT A 2 INCH ANSI 600 BALL VALVE ON THE BOTTOM OF THE MADILL PIG RECEIVER WAS FOUND WITH A SMALL ICE BALL ON DECEMBER 3, 2014. THE STATION HAD PREVIOUSLY BEEN INSPECTED ON NOVEMBER 17, 2014 WITH NO INDICATIONS OF A HYDROCARBON RELEASE. THE BALL VALVE IS A TWO-PIECE DESIGN AND WAS LEAKING IN BETWEEN THE MATING SURFACES. UPON DISCOVERY THE VALVE WAS ISOLATED AND REPLACED. ONEOK BELIEVES THE PRODUCT LEAKED FROM THE BALL VALVE INTO GROUND AND CAUSED THE HYDROCARBON VAPORS. SOIL CONTAINING HYDROCARBONS THAT HAD BEEN EXCAVATED DURING THE INVESTIGATION HAVE BEEN ANALYZED AND DETERMINED TO BE SAFE. ONEOK CONTINUES TO MONITOR THE LOCATION AND HAS NO INDICATIONS OF A RELEASE.