KATY STORAGE & TRANSPORTATION LP — Gas transmission and gathering — incident on 2014-12-23

Gas transmission and gathering incident in Not Within a Municipality, FORT BEND COUNTY County, TX. Reported cause: OTHER INCIDENT CAUSE. Reported consequences: 0 fatalities, 0 injuries, 0.19 NATURAL GAS released, $0 reported property damage. Operator-reported incident data submitted to PHMSA, generally within 30 days. Records may be supplemented or corrected and do not represent final agency causal findings.

Report number: 20150008.

Operator ID: 31705.

Reported incident date: 12/23/2014 10:46.

Location detail: KATY FACILITY

Cause detail: MISCELLANEOUS

Cause detail: ON DECEMBER 23, 2014, AT 10:46 AM, THE ENSTOR KATY GAS STORAGE FACILITY WAS ON INJECTION MODE USING TWO COMPRESSORS TO INJECT NATURAL GAS INTO THE RESERVOIR VIA 3 STORAGE WELLS AND 2 COMPRESSORS. ENSTOR PERSONNEL WERE PERFORMING MAINTENANCE ON THE PLC WHEN A LINE OF LOGIC (WHICH CONTAINED A TYPO) WAS SAVED TO THE NEW MASTER CONTROL CENTER (MCC) PLC. THIS CAUSED A PLC FAULT WHICH IN TURN CAUSED THE FACILITY TO ESD, AS DESIGNED. THIS ESD CORRECTLY ACTED TO FULLY BLOCK AND BLEED AND FLARE-TO-VENT, HOWEVER A CONTROL VALVE ON THE VENT SIDE FAILED TO OPEN CAUSING AN OVERPRESSURE EVENT WHICH RELIEVED VIA A PRESSURE RELIEF VALVE, AS DESIGNED. ENSTOR RESPONDED TO PUBLIC INQUIRIES REGARDING THE GAS RELEASE AND RESULTING NOISE. THESE CALLS WERE FROM THE PUBLIC, REGULATORS AND FIRST RESPONDERS. CALLS REPORTING SMOKE AND FIRE WERE EXPLAINED TO BE ONLY LOUD NOISE, DUST AND DEBRIS FROM THE PSV LINE. A PLANT INVESTIGATION PROCESS WAS INITIATED AND COMPLETED. THE ORIGINAL CAUSE WAS DETERMINED TO BE A FAULT IN THE PLC. UPON INVESTIGATING WHY THE FLARE/VENT LINE HAD NOT RELEASED, IT WAS DISCOVERED THAT THE VENT BLOCK VALVE HAD FAILED TO OPEN CAUSED BY A FAULTY VERSA VALVE (NV-105B). THE FAULT WAS IMMEDIATELY CLEARED AND CORRECTED IN THE PLC WITH CORRECT LOGIC, AND THE VERSA VALVE WAS REPLACED. THIS EVENT DOES NOT MEET THE INCIDENT REPORTING REQUIREMENTS AS DEFINED IN 49 CFR 191.3.1(I), 191.3.1(II), 191.3.1(III), OR 191.3. THIS INCIDENT REPORT HAS BEEN COMPLETED AND SUBMITTED AT THE REQUEST OF PHMSA SOUTHWEST REGION DUE TO A CALL FROM A LOCAL RESIDENT WHO LIVES CLOSE TO THE KATY GAS STORAGE FACILITY. THE TOTAL RELEASE TIME WAS APPROXIMATELY 40 SECONDS WITH AN ESTIMATED RELEASE VOLUME OF 197,000 SCF OF NATURAL GAS.

PHMSA trend classification: not significant, not serious.

PHMSA standardized cause: ALL OTHER CAUSES — MISCELLANEOUS.

PHMSA indexed costs: $581 reported total cost, $401.918 in 1984 dollars, $493.494 in current-year dollars.

PHMSA trend flags, standardized causes, and indexed costs are analytical fields added to operator-reported incident data. They do not represent final agency causal findings.