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Root cause analysis of the leak at Southern California Gas Company’s (SoCalGas) Aliso Canyon Natural Gas Storage Facility that began on October 23, 2015, found the direct cause was a rupture of the outer 7-inch well casing due to microbial corrosion from the outside resulting from contact with groundwater, an independent researcher discovered.

The California Public Utilities Commission (CPUC) and the Department of Conservation’s Division of Oil, Gas, and Geothermal Resources (DOGGR) unveiled the results Friday.

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CPUC, in consultation with DOGGR and the federal Pipeline and Hazardous Materials Safety Administration, selected Blade Energy Partners in January 2016 to perform an independent analysis of the leak’s root cause.

• Among Blade’s findings:
• The leak’s direct cause was a rupture of the outer 7-inch well casing due to microbial corrosion from the outside resulting from contact with groundwater.
• SoCalGas did not conduct detailed follow-up inspections or analyses after previous leaks. Blade identified more than 60 casing leaks at Aliso Canyon before the October 2015 incident going back to the 1970s.
• SoCalGas lacked any form of risk assessment focused on well integrity management and lacked systematic practices of external corrosion protection and a real-time, continuous pressure monitoring system for well surveillance.
• Updated well safety practices and regulations adopted by DOGGR address most of the root causes of the leak identified during Blade’s investigation.

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While CPUC and DOGGR’s initial assessment is that measures taken to date address the Blade report’s findings and recommendations, the analysis will be used to further improve regulations and overall gas storage facility oversight practices as appropriate.

Blade’s report will also inform parallel investigations being conducted by the CPUC and DOGGR. Those investigations are focusing on overall well and field operations and are expected to be completed later this year. Technical expertise will be provided from the Lawrence Berkeley, Lawrence Livermore, and Sandia National Laboratories (National Labs).

Since the leak, the CPUC and DOGGR have taken steps to prevent a similar leak from occurring again, including DOGGR’s new regulations for all underground natural gas storage reservoirs. Enacted immediately after the leak began and made permanent on October 1, 2018, the regulations ensure that no single point of failure in a well can cause a release of gas into the atmosphere.

SoCalGas issued a statement Friday following the Blade report’s release:

“Blade’s report confirms SoCalGas complied with gas storage regulations in existence at the time of the leak. Blade also determined that SoCalGas’ current practices and new state regulations address most, if not all, of the causes identified in the report.

“The release of this report marks an important milestone in helping the region and California move forward from the Aliso Canyon natural gas leak. The leak was an industry-changing event resulting in the development and implementation of enhanced safety regulations and practices.”

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