PUBLIC SERVICE CO OF NORTH CAROLINA

Incident Narrative

THIS SUPPLEMENTAL AND FINAL REPORT WAS SUBMITTED ON JULY 13, 2022. AT APPROXIMATELY 9:30 AM, ON JUNE 13, 2020, DOMINION ENERGY NORTH CAROLINA RECEIVED A 911-CALL REPORTING AN EXPLOSION AT 1347 COURTLAND DRIVE IN RALEIGH, NC. 911 REPORTED TO DENC THAT AN EXPLOSION OCCURRED IN THE CRAWL SPACE OF THE HOME AT 1347 COURTLAND. DENC CREWS DID NOT OBSERVE ANY FIRE AT THE HOUSE. A CONTRACTOR WORKING FOR THE HOMEOWNER OF 1347 COURTLAND WAS REPORTEDLY INJURED AT THE SCENE WHEN THE EXPLOSION OCCURRED. AT THE TIME OF THE EXPLOSION, THE CONTRACTOR WAS IN THE CRAWL SPACE UNDERNEATH THE HOME PERFORMING WORK ON THE HOMEOWNER'S HVAC SYSTEM. THE CONTRACTOR WAS REPORTEDLY BURNED BY THE EXPLOSION AND TRANSPORTED TO THE LOCAL BURN HOSPITAL. FOUR NEIGHBORING HOMES, ALONG WITH 1347 COURTLAND, WERE ALL EVACUATED (I.E., 1345, 1347, 1349, 1401, 1403 COURTLAND). THE RESIDENTS OF 1401 AND 1403 COURTLAND WERE ALLOWED TO RETURN TO THEIR HOMES WITHIN DAYS OF THE INCIDENT. AS OF AUGUST 2020, THE RESIDENTS OF 1345 AND 1349 COURTLAND HAD RETURNED TO THEIR HOMES. THE HOME AT 1347 COURTLAND SUSTAINED STRUCTURAL DAMAGE AND IS NOT HABITABLE. ON THE DAY OF THE INCIDENT, DENC DISCOVERED A NATURAL GAS LEAK NEAR THE TRANSITION BETWEEN THE STEEL TAPPING TEE AND THE PLASTIC SERVICE LINE THAT SERVED 1345 COURTLAND. THE RESPONDING DENC CREW STOPPED THE LEAK BY RUNNING THE TAPPING TEE CUTTER DOWN. AS A PRECAUTION, THE TAPPING TEE AT 1347 COURTLAND WAS ALSO SHUT OFF BY RUNNING DOWN THE TAPPING TEE PERFORATOR/STOP FOR THE SERVICE LINE. BOTH SERVICES WERE LATER DISCONNECTED, AND STEEL CAPS WERE WELDED ON. SUBSEQUENTLY, DENC EXPOSED THE MAIN IN FRONT OF 1345, 1347 AND 1349 COURTLAND AND VERIFIED THERE WERE NO LEAKS. A PORTION OF THE STEEL TAPPING TEE AND PLASTIC SERVICE LINE TO 1345 COURTLAND WITH THE VERIFIED LEAK WAS REMOVED AND PRESERVED FOR FURTHER TESTING. A LEAK FLOW TEST USING COMPRESSED AIR WAS PERFORMED ON THE SUBJECT PIPE IN A LABORATORY SETTING ON NOVEMBER 5, 2020. AT 60.0 PSI, THE LEAK RATE WAS 66 SCFH OF AIR, WHICH CONVERTS TO APPROXIMATELY 89.2 SCFH OF NATURAL GAS. USING THIS LEAK RATE, DENC ESTIMATES THE AMOUNT OF LOST GAS TO BE 295.43 MCF AND THE COST OF LOST GAS TO BE $1,371. DENC RETAINED INVESTIGATORS WHO EXAMINED THE SCENE. THESE INVESTIGATORS OBSERVED OXY-ACETYLENE TANKS LAYING ON THEIR SIDE IN THE CRAWL SPACE OF 1347 COURTLAND AFTER THE INCIDENT. THE INVESTIGATORS ASSESSED BLAST DYNAMICS AND OBSERVED ISOLATED BURN DAMAGE. SPECIFICALLY, THEY FOUND LITTLE TO NO FLAME PROPAGATION. THE PHOTOGRAPHS AFTER THE INCIDENT DEMONSTRATE THAT NEITHER THE WOOD JOISTS IN THE CRAWL SPACE NOR THE FOAM INSULATION WERE BURNED. THESE FINDINGS SUGGEST IGNITION OF A DISCRETE AMOUNT OF GASEOUS FUEL. WHILE THE EXACT AMOUNT OF GAS CONSUMED IN THE INCIDENT IS INDETERMINABLE, DENC ESTIMATES THAT IT WAS LESS THAN 1 MCF. (NOTE: PART A.21C WILL ONLY ALLOW A MINIMUM OF 1 MCF TO BE ENTERED). THE INVESTIGATORS' GAS MIGRATION MODELING SUGGESTS THAT NEAR-ZERO GAS FLOW WOULD MIGRATE FROM THE SERVICE LINE FRACTURE TO THE FOUNDATION WALL OF THE HOME, EVEN WITH THE HIGHEST SIMULATED PERMEABILITY VALUES (I.E., 1.0X10-3 CM2). IN LIGHT OF THE PHYSICAL FINDINGS AND GAS MIGRATION MODELING RESULTS, INVESTIGATORS QUESTIONED WHETHER OTHER POTENTIAL CONTRIBUTING FACTORS MAY HAVE LED TO THIS INCIDENT. SPECIFICALLY, THE OXY-ACETYLENE TANKS AND RELATED EQUIPMENT, WHICH WERE IN THE CRAWL SPACE WHEN THE INVESTIGATORS FIRST ARRIVED ON SCENE AND IN USE BY THE HVAC CONTRACTOR AT THE TIME OF THE INCIDENT, LATER WENT MISSING AS OF AUGUST 3, 2020 AND HAVE NOT BEEN RECOVERED TO DATE. THE HVAC CONTRACTOR'S EMPLOYER CONFIRMED THAT THEY DID NOT MAINTAIN RECORDS FOR THE MISSING TANKS AND RELATED EQUIPMENT. DENC CLASSIFIES THE APPARENT CAUSE OF THIS INCIDENT AS UNKNOWN (PART G8). THIS CONCLUDES DENC'S INVESTIGATION INTO THIS INCIDENT. INITIAL NRC INCIDENT REPORT #1279507, WAS MADE ON 06/13/20 AT 12:52 ET 48-HOUR UPDATE NRC #1279640, WAS MADE ON 06/15/20 16:51 ET LDF 1345/306401 & 1347/306389