The infamous Cascadia Subduction Zone which lies along the Oregon Coast unleashes a megathrust earthquake, like the March 11, 2011, quake in Japan, every six hundred years or so. The Oregon Coast is overdue for a major seismic event but that hasn’t stopped a Canadian energy company, Veresen, Inc, (formerly Fort Chicago) from applying for permits to site a potential bomb on the North Spit of Coos Bay.

As bad as the radiation catastrophe at the Fukushima Daiichi nuclear power plant in Japan is and can be if a full meltdown cannot be averted, it will not explode like an atomic bomb. Natural gas liquids, on the other hand, if a fire breaks out to heat the storage tanks, will unleash a Boiling Liquid Expanding Vapor Explosion or BLEVE.

It is claimed within the industry that LNG, liquefied natural gas, does not burn. “As a liquid, LNG is not explosive. LNG vapor will only explode in an enclosed space within the flammable range of 5-15 percent.” However, there are circumstances such as spills or a series of cascading failures that might accompany an earthquake or tsunami that can lead to unconfined vapor cloud explosions and boiling liquid expanding vapor explosions. Dr. Jerry Havens, a chemical engineer writes in his reportAn Assessment of the Potential Hazards to the Public Associated with Siting an LNG Import Terminal in the Port of Long Beach

I believe that the potential danger to the public from LNG spills is mainly from the very large fires that could occur. I want to emphasize that I am talking about fires resulting from the spillage of several millions of gallons of LNG – a single tank on a typical LNG carrier contains six or more million gallons of liquefied natural gas. The fire from such a spill, if it occurred onto water and was therefore uncontained, would be very large, perhaps up to a half-mile in diameter, or larger if more of the containment system failed. We have no experience with fires this large, but we do know that they could not be extinguished, they would just have to burn themselves out, and the radiant heat extending outward from the fires edge could cause serious burns to people even at larger distances.
There are two ways that very large fires can follow a major LNG spill. If LNG is spilled it will rapidly evaporate and the vapors will mix with air to form a mixture which will burn in the concentration range of approximately 5% to 15% LNG vapor. Such mixtures of LNG vapor and air will inevitably form when LNG is spilled, and if an ignition source such as an open flame or spark are present, as would be highly likely to accompany the violent circumstances that would cause a major release, a large pool fire will result. However, if no ignition sources are present in the flammable gas mixture a vapor cloud will result, and the cloud will spread downwind from the spill until it either contacts an ignition source or becomes diluted below its flammable concentration – it will then disperse harmlessly.

During a “controlled” test in the late eighties to learn more about rapid phase transition (flameless explosion) hazards, the force of the expansion created a spark that ignited a vapor cloud

On August 29, 1987, at the U. S. Liquefied Gaseous Spills Test Facility (LGSTF) in Nevada, during the fifth test (in the Falcon Test series), involving a large volume (50 cubic meters or 13,000 gallons) spill of liquefied natural gas (LNG), large and violent rapid phase transitions (RPTs – liquid phase transforming to vapor phase) occurred and were followed by the self ignition of the natural gas vapor. The tests were done for the purpose of studying vapor dispersion and were therefore deliberately designed to avoid accidental fires. The Rapid Phase Transitions (RPTs) that occurred when the LNG contacted the water are believed to have thrown concrete blocks with such force as to (indirectly) cause a spark that ignited the vapor cloud. The fire that ensued burned very rapidly and dramatically. The 5th test was necessarily the last in the Falcon Series as the fire destroyed the testing facility.[6]

[6] “Report of the Investigation Board for the Unplanned Fire at the Liquefied Gaseous Fuels Spill Testing Facility on August 29, 1987”, U.S. Dept of Energy- Nevada Operations Office; NVO-319

Professor Havens is of the opinion that a vapor cloud is very likely to find a source of ignition.

Spilled LNG will evaporate rapidly due to high rates of heat transfer from the warm surroundings (primarily the earth’s surface) to the cold liquid. The vapor evolving from the liquid pool will mix with air to form a gas-air mixture which will burn in the concentration range of approximately 5% to 15% LNG vapor (the concentration range that is flammable for methane-air mixtures). Such mixtures of LNG vapor and air will inevitably form when LNG is spilled, and if an ignition source such as an open flame or spark is present at a location where the gas mixture is within the flammable range a large pool fire will result.

The video above explains more about how a BLEVE can occur when a series of cascading failures consistent with natural disasters and unplanned power outages take place.