CONSOLIDATED EDISON CO OF NEW YORK

Incident Narrative

ON 11/6/21 AT 07:26, CON EDISON'S GAS EMERGENCY RESPONSE CENTER (GERC) RECEIVED A REPORT FROM ITS CUSTOMER OPS. CALL CENTER OF A GAS ODOR INSIDE AND OUTSIDE OF A RESIDENTIAL BUILDING LOCATED AT 733 PARK AVE. THE GAS ODOR HAD BEEN REPORTED TO THE CALL CENTER BY AN OCCUPANT OF THE SAME BUILDING. THE AREA IS SUPPLIED BY A 6-INCH LOW-PRESSURE CAST IRON GAS MAIN (INSTALLED IN 1897) AND A 30-INCH STEEL GAS TRANSMISSION MAIN (INSTALLED IN 1959), AS WELL AS UNDERGROUND ELECTRIC FACILITIES. CON EDISON GAS DISTRIBUTION SERVICES (GDS) RESPONDED TO THE LOCATION, INVESTIGATED, AND REPORTED A TYPE 1 GAS LEAK, WITH A NATURAL GAS READING OF 0.4% DETECTED IN THE GAS POINT-OF-ENTRY (POE) AT 733 PARK AVENUE. ADDITIONALLY, GDS DETECTED NATURAL GAS READINGS OF 15% IN TWO NEARBY ELECTRIC SUBSURFACE STRUCTURES (SSS'S) MANHOLE #M41786 AND SERVICE BOX #12935; THE COVERS OF THOSE TWO SSS'S WERE REMOVE BY GDS FOR VENTING. THE GERC THEN INITIATED A CODE MURRE, NOTIFIED THE FDNY, AND DISPATCHED ADDITIONAL CON EDISON GDS SUPERVISION TO THE LOCATION. UPON FURTHER INVESTIGATION, GDS DETECTED NATURAL GAS READINGS OF 0.3% IN THE ATMOSPHERE OF TWO BUILDING BASEMENTS AT 106 & 110 E. 71ST STREET. GDS SEALED THE ELECTRIC POE'S TO THOSE BUILDINGS AND VENTED THE READINGS IN THE TWO BASEMENTS TO 0% WITH ASSISTANCE FROM THE FDNY. GDS REPORTED THAT ALL OTHER BUILDINGS AND ADJACENT SSS'S WERE CLEAR OF GAS READINGS, AND THAT ELECTRIC MH #M41786 AND SB #12935 HAD BEEN VENTED TO 0%. CON EDISON EMERGENCY GAS CONSTRUCTION PERSONNEL WERE DISPATCHED TO THE LOCATION TO PINPOINT THE SOURCE OF THE LEAK. ON 11/7/21 AT 00:50, EMERGENCY GAS CONSTRUCTION REPORTED FINDING A POTENTIAL LEAK ON THE 30-INCH TRANSMISSION MAIN AFTER DETECTING NATURAL GAS READINGS OF ~100% IN THE VICINITY OF THE MAIN. ALL ADJACENT SSS'S, BUILDINGS, AND PROTECTION TEST POINTS WERE CHECKED AND FOUND TO BE CLEAR OF GAS READINGS. THE TRANSMISSION MAIN WAS OPERATING AT ~300 PSIG. NO OUTAGES OR NEGATIVE GAS SYSTEM IMPACT WERE REPORTED. GAS TRANSMISSION ENGINEERING AND GAS CONTROL WERE NOTIFIED OF THE POTENTIAL TRANSMISSION MAIN LEAK. CONTINGENCY CASE 6-C WAS ESTABLISHED AND PUT INTO EFFECT, AND GAS OPERATIONS PERSONNEL WERE ASSIGNED TO STAFF MULTIPLE MAIN VALVES AS PART OF THE CONTINGENCY. GAS OPERATIONS CREWS REMAINED ON LOCATION AND MONITORED THE CONDITION THROUGHOUT THE NIGHT. ON 11/7/21 AT 13:49, TWO TRANSMISSION MAIN VALVES WERE CLOSED TO ISOLATE A SEGMENT OF THE 30-INCH TRANSMISSION MAIN DUE TO THE LEAK CONDITION, WHICH APPEARED TO PROGRESSIVELY WORSEN. THE ISOLATION OF THE TRANSMISSION MAIN INTERRUPTED SERVICE TO FIFTEEN (15) GAS SERVICES AND NINE HUNDRED THIRTY-TWO (932) CUSTOMERS. CON EDISON GAS CONTROL ISSUED A LIMIT WORK ORDER AND A CONDITION YELLOW SYSTEM STATUS. CONSTRUCTION ACTIVITIES BEGAN AND THE COATING ON THE TRANSMISSION MAIN WAS SAFELY REMOVED. ONCE FULLY EXPOSED, A LEAK WAS FOUND ON THE TRANSMISSION MAIN AT THE 1 O'CLOCK POSITION. A NITROGEN BARRIER WAS INSTALLED, AND A HIGH HAT (A PERMANENT STEEL CAP) WAS WELDED OVER THE LEAK THAT WAS FOUND ON THE BODY OF THE TRANSMISSION MAIN. A PRESSURE TEST WAS CONDUCTED, AND THE TEST PASSED. TRANSMISSION PRESSURE WAS REINTRODUCED TO THE MAIN UP TO FULL OPERATING PRESSURE (327 PSIG) AT 50 PSIG INCREMENTS WITH LEAK SURVEYS CONDUCTED OVER THE AFFECTED AREA AT EVERY INCREMENTAL PRESSURE INCREASE, WITHOUT ANY FURTHER LEAKS DETECTED. THE REPAIR PROCEDURE WAS SUCCESSFULLY COMPLETED, AND SERVICE WAS SAFELY RESTORED ON 11/9/21 AT 18:09. THE SUSPECTED CAUSE OF THE NATURAL GAS LEAK WAS A HIGH-PRESSURE STEAM LEAK THAT WAS BLOWING DIRECTLY ON THE GAS TRANSMISSION MAIN. THERE WERE NO REPORTED INJURIES OR EVACUATIONS ASSOCIATED WITH THIS INCIDENT. NOTIFICATIONS WERE MADE TO PSC, DEP AND PHMSA.