CENTERPOINT ENERGY - MISSISSIPPI RIVER GAS TRANSMISSION CORP

Incident Narrative

ON THE MORNING OF NOVEMBER 30, 2010 AT 0620 THE FIRE CHIEF FROM THE CITY OF MADISON CALLED MISSISSIPPI RIVER TRANSMISSION (MRT) SYSTEM CONTROL TO REPORT A GAS LEAK AT THE INTERSECTION OF WASHINGTON AVE. AND RACE ST. MRT'S SYSTEM CONTROLLER NOTIFIED FIELD PERSONNEL AND OUR FIRST RESPONDERS ARRIVED ON THE SCENE AT 0650. THERE WAS A WATER LEAK AT THIS SITE ALSO AND WE COULD NOT IMMEDIATELY CONFIRM THAT IT WAS A GAS LEAK. WE CLOSED THE INLET BLOCK VALVE (BV42311 AT STATION 00+01) AT 0725 ON LINE A-122. THE DOWNSTREAM BLOCK VALVE (BV42312 AT STATION 175+92) WAS CLOSED AT 0755 ON LINE A-122. WE MONITORED THE LINE PRESSURE AND CONFIRMED THAT WE WERE LEAKING GAS AT 0837 ON OUR PIPELINE. MRT'S CONTRACTOR BROUGHT IN A 6"" WATER PUMP TO REMOVE THE WATER AT 0930 SO WE COULD EXCAVATE THE AREA OF THE LEAK. THE WATER COMPANY WAS CALLED TO THE SCENE AND THEY DENIED THAT THEY HAD A LEAK. THERE WAS ALSO A LIFT STATION DRAINAGE LINE IN THIS AREA. IT WAS SHUT OFF. AT 1630 AFTER NOT MAKING MUCH PROGRESS IN THE WATER REMOVAL, THE WATER COMPANY WAS CALLED AGAIN. THEY ARRIVED AT 1745 AND CONFIRMED THAT THEY DID HAVE A LEAK. THE WATER LINE WAS SHUTOFF AND EXCAVATION WAS STARTED ONCE THE WATER WAS REMOVED. AT 2130 A 4 BOLT LEAK CLAMP WAS INSTALLED ON THE GAS LINE TO SEAL OFF THE LEAK CAUSED BY EROSION FROM THE WATER AND SANDY SOIL. POSITIVE PRESSURE WAS MAINTAINED ON THE PIPELINE TO PREVENT WATER FROM ENTERING THE PIPE. THE LINE WAS BLOWN DOWN TO PREPARE FOR REPAIRS AT A LATER DATE. THE WATER COMPANY FINISHED THEIR LEAK REPAIRS AT 0230 ON DECEMBER 1ST. WATER WAS CONTINUOUSLY PUMP FROM THE AREA UNTIL DECEMBER 3RD. MRT'S CONTRACT WELDERS STARTED FABRICATING THE REPLACEMENT PIPE AND FITTINGS AT THE COLUMBIA MEASURING STATION ON DECEMBER 1ST. ON DECEMBER 2ND, THE PIPE AND FITTINGS WERE TRANSPORTED TO THE CONTRACTORS WELDING SHOP TO FINISH THE FABRICATION AND X-RAY. AT THE LEAK SITE THERE WAS MORE EXCAVATION DONE AND A 20 FT. SECTION OF PIPE WAS REMOVED. FOREMAN PLUGS WERE INSTALLED IN THE ENDS OF THE PIPE TO PREVENT ANYTHING FROM ENTERING THE PIPELINE. AN 8 HOUR HYDROTEST WAS PERFORMED ON THE NEW PIPE AND FITTING ON DECEMBER 3RD. DECEMBER 4TH THE CONTRACTOR DUG OUT MORE DITCH AND STARTED TO MAKE THE WELDS ON THE REPLACEMENT PIPE AND FITTINGS. BOTH OF THE WELDS WERE X-RAYED AND PASSED THE X-RAY. ON DECEMBER 5TH, FINISHED DIGGING OUT THE DOWNSTREAM END OF THE LINE IN ORDER TO FINISH THE TIE-INS. THE WELDS FROM THE PREVIOUS DAY WERE BLASTED AND RECOATED. LINE WAS TIED-IN AT 1100. AFTER PASSING THE X-RAY, THE LAST WELD WAS BLASTED AND RECOATED. THE LINE WAS PURGED, LOADED, AND PLACED BACK IN SERVICE AT 1330 ON DECEMBER 5TH.