CONSOLIDATED EDISON CO OF NEW YORK

Incident Narrative

ON MARCH 6, 2012 AT 08:18 HRS A LEAK SURVEY CREW PERFORMING THEIR MOBILE SURVEY REPORTED TO THE GAS EMERGENCY RESPONSE CENTER (GERC) THEY RECEIVED 94% AT THE CURB LINE IN THE VICINITY OF A 12"" 245 PSI RATED, COUPLED TRANSMISSION MAIN INSTALLED IN 1947 IN FRONT OF 1060 KNOLLWOOD ROAD, GREENBURGH. THE PRESSURE AT THE TIME OF DISCOVERY OF THE LEAK WAS 204 PSI. ADDITIONALLY, THERE ARE (2) HIGH PRESSURE (60 PSI) DISTRIBUTION MAINS IN THE VICINITY. A 16"" HIGH PRESSURE STEEL (HP STL) MAIN INSTALLED IN 1999 IS LOCATED 3' WEST OF THE TRANSMISSION MAIN, AND APPROXIMATELY 30 FEET EAST OF THE TRANSMISSION MAIN, ON THE OPPOSITE SIDE OF THE STREET IS A 2"" HIGH PRESSURE POLYETHYLENE MAIN WHICH WAS ALSO INSTALLED IN 1999. WESTCHESTER GAS CONSTRUCTION AND ADDITIONAL CREWS RESPONDED AND CONTINGENCY VALVES WERE LOCATED. THE LEAK WAS INVESTIGATED AND TWO EXCAVATIONS OVER THE PARALLEL 16"" HP STEEL DISTRIBUTION MAIN REVEALED NO LEAKS. THE CONSTRUCTION SUPERVISOR REPORTED THAT IN THE SECOND EXCAVATION VISIBLE WATER BUBBLING FROM THE DIRECTION OF THE TRANSMISSION MAIN 30' NORTH OF THE NORTH BUILDING LINE OF # 1060 KNOLLWOOD RD. INDICATED A PROBABLE LEAK ON THE TRANSMISSION MAIN. CREWS CEASED EXCAVATING, AND THE LEAK DID NOT POSE AN IMMEDIATE HAZARD TO LIFE OR PROPERTY. CONTINGENCY VALVES WERE STAFFED THROUGHOUT THE NIGHT, AND THE EXCAVATION MONITORED FOR SAFETY. AN OPERATIONAL PLAN WAS DEVELOPED WHICH INVOLVED PRESSURE REDUCTION, ISOLATION OF THE AFFECTED SECTION AND SUBSEQUENT HAND EXCAVATION TO DETERMINE THE LOCATION OF THE LEAK. AN OPERATIONAL PLAN WAS DEVELOPED TO IDENTIFY THE NECESSARY STEPS TO ISOLATE THE TRANSMISSION MAIN TO REPAIR THE LEAK. ON MARCH 7, 2012 AT 10:03 HRS., THE TRANSMISSION MAIN WAS ISOLATED VIA SHUTDOWN AND PRESSURE REDUCTION BEGAN. AT 10:34 HRS., PRESSURE WAS REDUCED TO 60 PSI. THE MAIN WAS EXCAVATED AND AT 15:55 HRS. A VISUAL LEAK ON A 12"" COMPRESSION COUPLING WAS CONFIRMED TO BE THE SOURCE OF THE LEAK. THE MAIN WAS ABATED AND A WELDED REPAIR SLEEVE WAS INSTALLED TO SECURE THE LEAK. ALL TESTING OF THE SLEEVE WERE SUCCESSFUL. ON MARCH 8, 20112, PRESSURE RESTORATION IN THIS SEGMENT OF MAIN BEGAN AT 03:00 HRS. THE MAIN PRESSURE WAS RESTORED INCREMENTALLY AND LEAK SURVEY CHECKED THE SEGMENT OF MAIN INVOLVED AT EACH PRESSURE INCREASE. NO LEAKS WERE FOUND. AT 07:18 HRS. GAS CONTROL REPORTED PRESSURE IN AFFECTED SEGMENT OF MAIN WAS 227 PSI. PRESSURE CONTROL RETURNED REGULATOR GR-483 TO OPERATION. THERE WERE NO INJURIES OR EVACUATIONS REPORTED AND THE N.Y.S. PSC AND U.S. DOT WERE NOTIFIED. THIS WAS A SERIOUS LEVEL INCIDENT.