An independent geologic evaluation of the Santa Susana earthquake fault at the Aliso Canyon gas storage field is still needed despite California officials’ determination that the field is safeto resume operation. No consensus exists on the fault hazard and the risk as outlined in Los Angeles County’s recent legal action against the state. Neither the state nor the Southern California Gas Co. has sufficiently addressed the hazard created by all the wells at the field crossing the fault in the subsurface.
Could future fault movement damage many wells and release methane gas to the surface, creating a significant risk to public safety, the environment, and energy supplies worse than the massive 2015-16 blowout?
Neither the state nor SoCalGas has shown this is impossible or offered a mitigation and safety plan in case it happens.
The state and SoCalGas claimed there is no safety issue. But published geologic research shows the fault has a high movement-rate over recent geologic time, meaning it has likely experienced more frequent large earthquakes than most other faults in California.
The state claimed L.A. County was relying on “the vague possibility of a future, hypothetical catastrophic earthquake” to oppose gas injection. But this claim is inconsistent with the geologic facts.
Geology shows the fault hazard is neither vague nor hypothetical but is unique and clear, and needs further independent research.
Perhaps the state was relying on SoCalGas’ submitted Storage Risk Management Plan No. 2 of Oct. 11, 2016 — an incomplete and misleading document that seems to be SoCalGas’ only publicly available response to the hazard.
For 40 years of Aliso Canyono’s operation, L.A. County residents have not been informed of the fault hazard and risk. Regulators, as well as SoCalGas and its consultants, have had ample time — and in some cases the responsibility — to address such a threat.
In response to the 2015-16 blowout, the state’s Division of Oil and Gas and Geothermal Resources (DOGGR) and Public Utilities Commission, and the national Pipeline and Hazard Materials Safety Administration (PHMSA), seem ready to adopt new regulations more appropriate for Texas than seismically active California.
Recommended Practices (RP) 1171, developed by the American Petroleum Institute for gas storage wells and fields, declares: “Depleted hydrocarbon reservoirs are candidates for natural gas storage because the reservoir integrity has been demonstrated over geologic time by hydrocarbon containment at initial pressure conditions.” True, except gas wells have not existed over geologic time and are a weak link if subjected to fault movement.
RP 1171 insufficiently deals with the faulting hazard in earthquake-prone areas: In its 60 pages, faulting is mentioned once, earth movements twice and active faults never. Contrast this with the United States Nuclear Regulatory Commission’s entire publication devoted to earthquake and fault hazards, called Seismic and Geologic Siting Criteria for Nuclear Power Plants. PHMSA now proposes that RP 1171 be mandated for the nation’s gas storage wells, and DOGGR proposes it for California.
Did the state rely on its in-house fault hazard experts, the California Geologic Survey (CGS), for any advice or to support its court claims? State law, via the Alquist-Priolo and Fields Acts, and enforced and advised by the CGS, ban or limit construction of habitable structures and schools over portions of the Santa Susana fault. An odd regulatory situation has emerged that recognizes a fault rupture hazard at the Earth’s surface — but not high-pressure gas wells crossing faults in the subsurface.
That’s an untenable position with respect to geology, where surface rupture is derived from subsurface fault movement, coming from a deeper earthquake source. Fault hazards have become restricted by regulatory definition rather than geology determining what is a hazard. This undermines public safety.
One important lesson learned from the blowout at Aliso is that subsurface problems in gas wells can be much more difficult to control than leaks in surface pipelines. Yet the earthquake faulting hazard at the surface is regulated, and the subsurface faulting hazard to gas wells remains mostly ignored and unregulated.
The state claims that Aliso has received more scrutiny than any facility in the United States. This might be true when it comes to engineering, but it might also indicate that other gas storage fields have received limited scrutiny, especially in seismically risky areas.
Regardless, Los Angeles County has yet to see a truly independent geologic evaluation of the hazard and risk posed by the Santa Susana fault to the Aliso Canyon facility, and that and its regulatory history should be of paramount concern to the county’s residents.
Thomas L. Davis, a geologist, is director of the Geologic Maps Foundation, Inc.
