NSTAR GAS COMPANY

Incident Narrative

"3.31/25 UPDATED REPORT BASED ON PHMSA REQUEST A, B, C, D AND G BASED UPON THE INITIAL NARRATIVE PROVIDED BY THE MAYNARD FIRE DEPARTMENT TO EVERSOURCE, ON SEPTEMBER 2, 2021 AT 16:14, THE MAYNARD FIRE DEPARTMENT DISPATCHED RESOURCES TO 27 PARK ST MAYNARD, MA DUE TO AN ODOR CALL. THE MAYNARD FIRE DEPARTMENT ARRIVED ON SITE AT 16:17 TO A STRUCTURE FIRE. EVERSOURCE RECEIVED A CALL FROM THE MAYNARD FIRE DEPARTMENT AT 16:33 NOTIFYING EVERSOURCE OF THE SUBJECT STRUCTURE FIRE. EVERSOURCE COORDINATED WITH THE MAYNARD FIRE DEPARTMENT, MASSACHUSETTS STATE FIRE MARSHALL, AND STATE REGULATORY AGENCY ON SITE. THE SITUATION WAS MADE SAFE THROUGH A MAINLINE REPAIR ON SEPTEMBER 3, 2021. A SECTION OF THE MAIN WITH A COUPLING WAS SECURED AND DELIVERED TO THE MASSACHUSETTS MATERIAL RESEARCH FACILITY FOR 3RD PARTY ANALYSIS. MASSACHUSETTS MATERIAL RESEARCH'S INVESTIGATION OF THE GAS MAIN SEGMENT REVEALED SIGNIFICANT CORROSION ON THE ENTIRE OUTER DIAMETER SURFACE OF THE COUPLING TUBE FROM THE SOIL/DIRT SERVICE ENVIRONMENT. THE COUPLING SHOWED SIGNIFICANT WALL THINNING AT ISOLATED LOCATIONS. AT THESE ISOLATED SPOTS ON THE COUPLING, THE PITS BREACHED THROUGH THE WALL THICKNESS, WHICH CREATED A LEAK PATH FOR THE GAS TO ESCAPE FROM THE INSIDE OF THE GAS MAIN. MASSACHUSETTS MATERIAL RESEARCH FOUND THE GAS MAIN TO BE IN SIGNIFICANTLY GOOD CONDITION WITHOUT ANY ANOMALIES THROUGH THE ENTIRE LENGTH OF THE PIPE SEGMENT. PART A.4, A.12 THIS WAS THE TIME THE COMPANY COMMENCED A LEAK INVESTIGATION DURING WHICH GAS READINGS WERE DETECTED. PART A.21 THE COMPANY RESPONDED YES BASED UPON THE INITIAL NARRATIVE PROVIDED BY THE MAYNARD FIRE DEPARTMENT AND GAS READINGS FOUND IN NEAR PROXIMITY TO THE STRUCTURE FIRE. PART A.21.A THE TIME THE MAYNARD FIRE DEPARTMENT ARRIVED ON SITE TO A STRUCTURE FIRE. PART A.21.D PER ""SECTION III. CONCLUSION"" OF THE MASSACHUSETTS FIRE DISTRICT FOURTEEN'S REGIONAL FIRE INVESTIGATION TEAM FIRE ORIGIN AND CAUSE INVESTIGATION REPORT, ISSUED TO EVERSOURCE ON OCTOBER 13, 2021, ""THE MOST PLAUSIBLE HYPOTHESIS IS THAT OF FUEL GAS EXPLOSION. IT IS BELIEVED TO BE AN ACCIDENTAL LOW ORDER FUEL GAS EXPLOSION CAUSED [THE] FIRE."" PART A.7,A.21.C, D2.F VALUES DEFAULTED TO 1 AND 0. THE AMOUNT OF GAS RELEASE IS UNKNOWN AT THIS TIME. PART D.2.A THE PUBLIC AND NON-OPERATOR PRIVATE PROPERTY DAMAGE IS CURRENTLY BASED ON A PROPERTY ASSESSMENT PROVIDED BY THE FIRE DEPARTMENT AS WELL AS COSTS ASSOCIATED WITH LANDSCAPING, PAVING AND CONCRETE. HAS BEEN UPDATED TO REFLECT BUILDING AND ITS CONTENTS ESTIMATE. PART D.2.B THE REPAIR COST INCLUDES THE REPAIR COSTS AS WELL AS THE FOLLOW UP LEAK SURVEY COSTS PART E.2 AN AVERAGE OPERATING PRESSURE WAS OBTAINED PRIOR TO THE INCIDENT. PART E.3.B THE MAIN WAS INSTALLED IN 1968 PRE-CODE. THE DATE FOR MAOP WAS DEFAULTED TO 7/1/1970 AS THAT WAS WHEN 192.619(C) WAS ESTABLISHED. PART E.5 THE DRIP REFERENCED IS A DRIP ODORIZER - Z9000. PART E.6 THE COMPANY TOOK MULTIPLE READINGS NONE OF WHICH REACHED OR EXCEEDED 0.15%. THE READING PROVIDED WAS THE FIRST READILY DETECTABLE LEVEL RECORDED AT 0.07. THIS REPORT FUNCTIONALITY ROUNDED THE NUMBER UP TO 0.1. PART G.5 - CORROSION WAS ON COUPLING NOT ON PIPE."