MID-CONTINENT FRACTIONATION AND STORAGE, L.L.C.

Incident Narrative

AT APPROXIMATELY 1123 HOURS ON JANUARY 11, 2016, OPERATIONS IDENTIFIED A RELEASE OF NATURAL GAS LIQUID (NGL) FROM A VALVE ON A DEAD-LEG PRODUCT LINE NEAR CAVERN 33 AT THE CONWAY WEST FACILITY. THE PRODUCT LEAKING WAS IDENTIFIED AS NORMAL BUTANE. THE LINE WAS BLOCKED IN, EMERGENCY SERVICES WERE OBTAINED, AND THE RESIDUAL BLOWDOWN FROM THE ISOLATED LINE WAS MONITORED UNTIL COMPLETE AND VAPORS WERE CLEAR IN THE AREA. THE RELEASE OF BUTANE WAS THE RESULT OF DAMAGE TO AN ABOVE GROUND 8"" VALVE, WHICH RELEASED LIQUID BUTANE, WHICH WAS CONVERTED TO VAPOR WHEN RELEASED TO ATMOSPHERE. THE VOLUME OF BUTANE LIQUID RELEASED TO ATMOSPHERE IS ESTIMATED AT 140 BARRELS. WATER VAPOR WAS FROZEN AT THE LEAK LOCATION AND ALONG THE FROZEN GROUND SURFACE. THE LINE WAS ISOLATED AT 1145 HOURS. LEL MONITORS WERE SET AT 1203 HOURS TO MONITOR FOR AIR IMPACTS IN THE RELEASE AREA. INITIAL ROAD BLOCKS WERE SET AT 1130 HOURS ON JANUARY 11, 2016 AS A PRECAUTIONARY MEASURE NEAR THE LEAK LOCATION (JUST NORTH OF HWY 56 AND WEST OF 5TH AVENUE). THE LEAK WAS COMPLETELY CONTAINED BY 0606 HOURS JANUARY 12, 2016. THE HIGHWAY WAS REOPENED FOR PUBLIC TRAFFIC BY THE FIRE DEPARTMENT AT 0630 HOURS JANUARY 12, 2016. RESULTS OF THE INVESTIGATION REVEALED THAT WATER TRAPPED INSIDE OF THE VALVE ON A DEAD LEG FROZE CAUSING EXPANSION WITHIN THE VALVE BODY LEADING TO THE SPLIT BODY VALVE BEING OPENED AT THE BOLTED SEAM CONNECTION. THE RESIDUAL WATER REMAINED FROM A PREVIOUS HYDROSTATIC TEST IN AUGUST OF 2015. THE VALVE WAS PARTIALLY OPEN DURING TESTING AS PER PROCEDURE, HOWEVER AT THE CONCLUSION OF THE TEST, DEWATERING PRACTICES DID NOT SUFFICIENTLY REMOVE THE WATER FROM INSIDE THE VALVE AT THE END OF THE DEAD LEG. THE VALVE WAS SUBSEQUENTLY CLOSED AND RETURNED TO SERVICE. FIVE MONTHS LATER THE LEAK OCCURRED DURING FREEZING WEATHER. WHEN THE WATER TRAPPED INSIDE THE VALVE FROZE, THE EXPANSION CAUSED PRODUCT TO SEEP PAST THE VALVE SEAT TO THE LOW PRESSURE SIDE, ESCAPING THROUGH THE SPLIT SEAM CAUSING ADDITIONAL FREEZING AND EXPANSION. CORRECTIVE ACTIONS: - THE DEAD LEG SEGMENT WAS REMOVED. - SITE SPECIFIC PURGE AND PACK PROCEDURES HAVE BEEN PREPARED THAT ADDRESS MORE DETAILED DEWATERING PROVISIONS. - A WILLIAMS INTERNAL CONTINUOUS IMPROVEMENT ADVISORY BULLETIN WILL BE PREPARED AND COMMUNICATED TO ALL OPERATING AREAS AND ENGINEERING AND CONSTRUCTION GROUPS. - THE CONTINUOUS IMPROVEMENT ADVISORY BULLETIN WILL INCLUDE REQUIREMENTS TO REVISE APPLICABLE O&M PROCEDURES AND CONSTRUCTION STANDARDS WITH POST HYDROSTATIC TEST DEWATERING METHODS. - PROVISIONS FOR REMOVAL OF DEAD LEGS DURING PROJECTS INVOLVING APPLICABLE MODIFICATIONS WILL ALSO BE INCLUDED IN THE ADVISORY.