TRANSCONTINENTAL GAS PIPE LINE COMPANY

Incident Narrative

PLEASE REFERENCE THE ORIGINAL REPORT NO. 20180051-30306 DATED AND FILED ON 05/11/2018 FOR THE INITIAL INCIDENT REPORT INFORMATION AND DETAILED TIME LINE OF EVENTS FOR THIS INCIDENT. A BRIEF SUMMARY IS DESCRIBED BELOW. ON 04/12/2018 AT APPROXIMATELY 1:00 PM (13:00), A LEAK WAS DISCOVERED NEAR MLV 135D10 AND EVENTUALLY DETERMINED TO BE ON THE ON THE DOWNSTREAM SIDE OF THE VALVE. OPERATIONS PERSONNEL MOBILIZED TO THE SITE AND BEGAN TO ISOLATE THE VALVE SEGMENTS AT 2:00 PM (14:00), AND THEN THE BLOW DOWN FROM MLV 135D10 TO MLV 135D20 WAS COMPLETED ON 04/13/2018 AT 12:00 PM (12:00). PIPELINE SAFETY REVIEWED THE EVENT AND DETERMINED THE NRC SHOULD BE CONTACTED SINCE THE REPAIR COST WILL EXCEED $50,000. THE NRC WAS INITIALLY CONTACTED AT 2:02 PM (14:02), UNDER NRC# 1209263. ON 04/20/2018 AT 12:37 PM (12:37), THE NRC WAS CONTACTED TO UPDATE THE INCIDENT, UNDER NRC# 1209842. PHMSA REQUESTED CORRECTIONS TO THE ORIGINAL REPORT AND PREVIOUS ILI DATA FOR REVIEW ON 05/18/2018, AND ON 05/21/2018 PHMSA REQUESTED THAT ALL COSTS ASSOCIATED WITH THE VALVE REPLACEMENT MUST BE REPORTED. THIS FINAL INCIDENT REPORT UPDATES THE COMPLETED VALVE REPLACEMENT WORK, INCLUDES THE ASSOCIATED COSTS, REQUESTED CORRECTIONS, INCLUDES THE PREVIOUS 2014 ILI DATA SUMMARY AS DESCRIBE BELOW, AND INCLUDES A SUMMARY OF THE FINDINGS FROM THE METALLURGY LABORATORY ANALYSIS OF THE CRACKED WELD JOINT BETWEEN THE PREVIOUS 36-INCH MAINLINE BLOCK VALVE (MLV 135D10) AND THE REDUCER (42 IN. X 36 IN.). THE EXISTING 36-INCH MAINLINE BLOCK VALVE AND REDUCER WERE ALREADY SCHEDULED FOR REPLACEMENT WITH A NEW 42-INCH VALVE AND PIPE WHEN THE GAS LEAK INCIDENT OCCURRED. THE EXISTING 42-INCH PIPELINE SEGMENT WAS KEPT OUT OF SERVICE UNTIL THE NEW VALVE AND PIPE COULD BE SCHEDULED FOR REPLACEMENT AS PLANNED. THE VALVE REPLACEMENT WORK BEGAN ON 06/05/2018. THE NEW 42-INCH VALVE AND PIPE WERE INSTALLED AND THE EXISTING 42-INCH PIPELINE SEGMENT WAS PLACED BACK INTO SERVICE ON 07/12/2018 AT APPROXIMATELY 2:30 PM EST (14:30). THE EXISTING 36-INCH VALVE AND REDUCER WERE CUT-OUT AND THEN SENT TO HERRERA, STAFFORD & ASSOCIATES (HSA) FOR ANALYSIS ON OR ABOUT 07/24/2018. WILLIAMS PROVIDED PHMSA AN EMAIL UPDATE STATUS ON 07/27/2018. ON 11/08/2018, HAS ISSUED THE FINAL METALLURGICAL EVALUATION FOR THE CRACKED GIRTH WELD SECTION BETWEEN THE EXISTING MLV 135D10 VALVE AND REDUCER. THE METALLURGICAL EXAMINATION DETERMINED THE CRACK-LIKE INDICATION WAS A TOE CRACK OBSERVED ON THE REDUCER SIDE OF THE GIRTH WELD. ELEVATED HARDNESSES, MARTENSITE, AND SECONDARY INTERGRANULAR CRACKS INDICATE THE CRACK WAS LIKELY THE RESULT OF HYDROGEN ASSISTED CRACKING IN THE HEAT AFFECTED ZONE OF THE WELD (ALSO KNOWN AS HYDROGEN-INDUCED TOE CRACKING OR COLD CRACKING). THE CRACK MEASURED 16-INCHES ON THE OD SURFACES AND WAS THROUGH WALL FOR 6.75 INCHES. THE RECENT ILI (MFL) TOOL RUN WAS PERFORMED ON 10/30/2014 FROM OUR COMPRESSOR STATION 130 TO COMPRESSOR STATION 140, AND INCLUDED THE MLV 135D10 VALVE SITE LOCATION. THE PREVIOUS ILI DATA WAS REVIEWED 500-FEET UPSTREAM AND DOWNSTREAM FOR THIS LOCATION, AND INDICATED 10% TO 20% WALL LOSS WITH A PBURST THAT VARIED FROM 1.99 TO 2.40. THESE FEATURES WOULD NOT HAVE BEEN CLASSIFIED AS ANOMALIES FOR INVESTIGATION. THE INITIAL ILI (MFL) BASELINE ASSESSMENT WAS PERFORMED ON 12/17/2007. ALL THE INFORMATION WAS GATHERED AND VERIFIED WITH CORRECTIONS, AND A FINAL INCIDENT REPORT WAS SUBMITTED ON 12/14/2018. PHMSA RETURNED COMMENTS AND CORRECTIONS TO THE FINAL REPORT ON 01/04/2019. A REVISED FINAL INCIDENT REPORT WAS SUBMITTED ON 01/29/2019 WITH THE CORRECTIONS MADE.