CONSOLIDATED EDISON CO OF NEW YORK

Incident Narrative

ON MARCH 23, 2018, A MAIN VALVE INSPECTION WAS PERFORMED THAT INCLUDED A FULL REMOTE CLOSURE INSPECTION OF REMOTELY OPERATED VALVE (ROV) 62190, LOCATED IMMEDIATELY DOWNSTREAM OF THE TRANSCO (PIPELINE) 134TH STREET CITY GATE STATION IN MANHATTAN. THIS INSPECTION WAS PERFORMED BY CON EDISON GAS OPERATIONS PRESSURE CONTROL PERSONNEL WITH ASSISTANCE FROM INTERSTATE TRANSMISSION PIPELINE COMPANY PERSONNEL, WHO WERE ALSO ON SITE. PRIOR TO THE INSPECTION, THE CITY GATE STATION WAS FLOWING AT 13,000 DEKATHERMS PER HOUR AT AN OUTLET PRESSURE OF 287 PSIG INTO CON EDISON'S TRANSMISSION SYSTEM. AT 01:51, ALL PERSONNEL WERE ON SITE AND READY TO BEGIN THE INSPECTION ACTIVITIES, AT WHICH TIME CON EDISON'S GAS CONTROL GROUP BEGAN COORDINATING THE SHUTDOWN OF THE CITY GATE STATION WITH THE PIPELINE'S GAS CONTROL GROUP. AT 02:05, CON EDISON'S GAS CONTROL GROUP CONFIRMED WITH PIPELINE ON-SITE PERSONNEL THAT THE CITY GATE STATION WAS FULLY SHUTDOWN, WHICH HAD BEEN ACCOMPLISHED BY CLOSURE OF THE STATION METER RUNS MANUAL OUTLET VALVES. AT 02:08, AFTER BEING NOTIFIED THAT THE GATE STATION WAS FULLY SHUTDOWN, CON EDISON PRESSURE CONTROL PERSONNEL BEGAN PERFORMING THE MANUAL OPERATION PORTION OF THE ROV INSPECTION, WHICH WAS COMPLETED AT 02:09. CON EDISON PRESSURE CONTROL PERSONNEL THEN BEGAN PERFORMING THE REMOTE OPERATION PORTION OF THE ROV INSPECTION. AT 02:10, THE STATION OUTLET PRESSURE FELL BELOW 250 PSIG. AT 02:17, THE REMOTE OPERATION PORTION OF THE INSPECTION WAS COMPLETED, THEREBY CONCLUDING ALL TASKS ASSOCIATED WITH THE PLANNED ROV INSPECTION. AT 02:21, AN ON-SITE PIPELINE TECHNICIAN REQUESTED THAT CON EDISON GAS CONTROL CLOSE ROV 62190 DUE TO ACTIVATION OF THE STATION'S UNDER-PRESSURE PROTECTION, EQUIPMENT DESIGNED TO MAINTAIN A MINIMUM PRESSURE IN THE DOWNSTREAM PIPING, WHICH HAD ENGAGED WHEN THE STATION OUTLET PRESSURE FELL BELOW 250 PSIG. THE PIPELINE TECHNICIAN'S PLAN WAS TO INCREMENTALLY OPEN THE METER RUN #1 ISOLATION VALVE TO RAISE THE DOWNSTREAM PRESSURE ABOVE 250 PSIG, WHICH WOULD CAUSE THE UNDER-PRESSURE PROTECTION TO DISENGAGE AND THE REGULATOR RUNS TO CLOSE AUTOMATICALLY. CON EDISON GAS CONTROL WOULD THEN BE NOTIFIED TO RE-OPEN ROV 62190. AT 02:22, CON EDISON GAS CONTROL CLOSED ROV 62190. AT 02:23, CON EDISON GAS CONTROL NOTIFIED THE PIPELINE TECHNICIAN THAT THE ROV WAS CLOSING. THE PIPELINE TECHNICIAN RESPONDED INDICATING THAT, ONCE THE ROV WAS CLOSED, HE WOULD PROCEED TO OPEN THE MANUAL ISOLATION VALVE A SMALL AMOUNT TO INCREASE THE DOWNSTREAM PRESSURE. AT 02:26, CON EDISON GAS CONTROL RECEIVED A ""HIGH-HIGH"" PRESSURE ALARM AT THE GATE STATION, AND AT 02:27, THE PIPELINE TECHNICIAN NOTIFIED CON EDISON GAS CONTROL THAT ROV 62190 COULD BE RE-OPENED. AT 02:28, CON EDISON GAS CONTROL BEGAN SLOWLY OPENING ROV 62190 IN 10% INCREMENTS, WHICH CLEARED THE ""HIGH-HIGH"" PRESSURE ALARM AT 02:29. CON EDISON GAS CONTROL DETERMINED POST INCIDENT THAT THE MAXIMUM ALLOWABLE OPERATING PRESSURE (MAOP) OF THE CON EDISON OWNED SEGMENT OF TRANSMISSION PIPELINE IMMEDIATELY UPSTREAM OF THE ROV HAD BEEN EXCEEDED FOR APPROXIMATELY 2 MINUTES, DURING WHICH THE PRESSURE PEAKED AT 478 PSIG AT 02:28. INTERNAL NOTIFICATIONS WERE MADE AT 03:22, AND CON EDISON NOTIFIED THE NEW YORK PUBLIC SERVICE COMMISSION AND THE NATIONAL RESPONSE CENTER AT 03:52. TO PREVENT FUTURE RE-OCCURRENCE OF A SIMILAR EVENT, INTERNAL COMPANY OPERATING SPECIFICATIONS ARE BEING REVISED TO REQUIRE GAS ENGINEERING OVERSIGHT IN THE FORM OF WRITTEN WORK PROCEDURES FOR ROV'S LOCATED ON THE OUTLET OF CITY GATES AS WELL AS THE ELIMINATION OF FULL OPERATION TESTING TO BETTER ALIGN WITH REGULATORY REQUIREMENTS.