GULF SOUTH PIPELINE COMPANY, LLC

Incident Narrative

ON 6/1/2023 AT APPROXIMATELY 10:30 AM, GULF SOUTH PIPELINE COMPANY LLC'S OPERATIONS PERSONNEL WERE ALERTED BY ENTERPRISE PRODUCTS PERSONNEL THAT ENTERPRISE'S WELL 11, WHICH IS ADJACENT TO GULF SOUTH'S PETAL GAS STORAGE NATURAL GAS CAVERNS PGS 10 AND PGS 12A, WAS EXPERIENCING AN INCREASE IN PRESSURE RESULTING IN A SURFACE LEAK. GULF SOUTH WAS NEITHER INJECTING NOR WITHDRAWING GAS FROM WELLS PGS 10 OR PGS 12A, AND DECIDED NOT TO DO SO UNTIL THE PRESSURE ON ENTERPRISE'S WELL 11 HAD STABILIZED. ON 6/2/2023 AT APPROXIMATELY 7:10 AM, GULF SOUTH AND ENTERPRISE DETERMINED THAT THE SURFACE LEAK ON ENTERPRISE'S WELL CONTAINED METHANE AND THAT A POSSIBLE SOURCE OF THE METHANE WAS EITHER CAVERN PGS 10 OR PGS 12A COMMUNICATING WITH ENTERPRISE'S WELL 11 BELOW GROUND, IN THE SALT FORMATION. BECAUSE OF THIS POSSIBILITY, GULF SOUTH CALLED THE NRC. DURING THE INVESTIGATION OF THIS EVENT, GULF SOUTH IDENTIFIED THAT THE MAOP OF CAVERN PGS 10, WHICH IS 1550 PSIG AT THE SURFACE, INCREASED TO 1564 PSIG WITHOUT INJECTION OF GAS, AROUND THE SAME TIME OF THIS INCIDENT. GULF SOUTH PULLED GAS OUT OF BOTH CAVERNS PGS 10 AND PGS 12A OVER THE NEXT SEVERAL DAYS WHILE STAYING IN CONTACT WITH ENTERPRISE AND ENTERPRISE'S PRESSURE STABILIZED AFTER DOING SO. PER BOARDWALK'S (GULF SOUTH'S) WELL CONTROL ERP, GULF SOUTH DECLARED A LEVEL 2 WELL CONTROL INCIDENT ON 6/2/2023 AT APPROXIMATELY 7:00 AM, DOWNGRADED THE INCIDENT TO A LEVEL 1 ON 6/3/2023 AT 8:15 AM, AND CLOSED THE INCIDENT ON 6/7/2023 AT 9:15 AM. ADDITIONALLY, OUT OF AN ABUNDANCE OF CAUTION, GULF SOUTH HAS PERFORMED A MECHANICAL INTEGRITY TEST ON CAVERN PGS 12A AS WELL AS MULTIPLE PRESSURE, TEMPERATURE, AND DENSITY LOGS ON BOTH CAVERNS. THE RESPONSE TO QUESTION B10A OF THIS REPORT IS SHOWN AS, ""ONE INCH DEPTH OF COVER."" THE LIMITATIONS OF THE REPORTING SYSTEM PROHIBIT ENTRY OF AN ACCURATE RESPONSE. THE CAVERN ROOF OF PGS 10 IS 2,163 FEET (25,956 INCHES) AND PGS 12A IS 4,284 FEET (51,408 INCHES) BELOW THE SURFACE. THE RESPONSE TO QUESTIONS C4 AND C5 REFLECTS THE COMPLETION DATE OF CAVERN PGS 10; IT IS THE EARLIER OF THE TWO CAVERN COMPLETION DATES. THE COMPLETION DATE OF PGS 12A IS 7/22/2008. THE RESPONSE TO QUESTION D3 REPRESENTS THE PIR OF CAVERN PGS 12A (THE LARGER OF THE TWO MAOPS). ADDITIONALLY, THE MAOP OF PGS 10 IS 543 FEET. THE RESPONSE TO QUESTION E2 REPRESENTS THE MAOP OF CAVERN PGS 10; ADDITIONALLY, THE MAOP OF CAVERN PGS 12A IS 3181 PSIG. THE RESPONSE TO QUESTION E2B SHOWS THE MAOP ESTABLISHED DATE FOR CAVERN PGS 10. ADDITIONALLY, THE MAOP ESTABLISHED DATE FOR PGS 12A IS 7/22/2013. THE RESPONSE TO QUESTION E3 SHOWS THAT THE PRESSURE EXCEEDED THE APPLICABLE ALLOWANCE IN