BLAST RISK
Experts say ‘vapor cloud explosions’ pose far greater danger than regulators and companies have long believed
Experts raise concerns about underestimated danger at LNG plants.
As fracking turned the United States into a major producer of natural gas over the past decade, federal regulators approved the construction of export terminals along the Atlantic and Gulf coasts while relying on industry safety calculations that critics say significantly understate the potential force of a specific type of accidental explosion.
The particular event that worries engineers outside the business has a very low probability of happening but could have exceedingly destructive consequences if it does.
Under new leadership since January, the federal Pipeline and Hazardous Materials Safety Administration, or PHMSA, said it intends to draw up rules at some point next year that would deal with the risk in question.
The move comes as two new plants just outside Brownsville are poised to begin construction. Yet each has already passed through the safety permitting process.
Critics have argued since 2016 that the industry’s calculations seriously underestimate the destructive potential of what engineers call a vapor cloud explosion. Over the years, those arguments have been enhanced by greater specificity and greater documentation.
The danger is not what you might suppose: It’s not the natural gas, though that also poses risks. The threat of a vapor cloud explosion comes from the heavier hydrocarbons used to chill the natural gas so deeply that it turns into a liquid, which is then loaded onto ships for sale abroad. These hydrocarbons are called refrigerants, and under the right conditions, a major leak of volatile refrigerants on a windless day could lead to the buildup of a cloud of ground-hugging vapor, until a spark sets it off.
The model used by the industry, and implicitly accepted by PHMSA, has held in case after case that the destructive force of a vapor cloud explosion would be spent by the time it reaches the perimeter of whatever terminal is under consideration. But specialists not associated with the gas business say this is wrong.
One study by British experts found that a hypothetical vapor cloud explosion could be up to 15 to 20 times as powerful as what the planners modeled.
Jared Hockema is the city manager of Port Isabel, a community of 6,000 east of Brownsville that relies on sport fishing and commercial shrimping for its livelihood. From his office just steps from Laguna Madre, the bay that separates the mainland from South Padre Island, it is a mile and a half back through town to the Brownsville-Port Isabel Highway.
There, just behind the HE-B Supermarket, on flat reclaimed scrubland between a lake named Vadia Ancha and the Brownsville Ship Channel, a company called Texas LNG wants to build an export terminal.
Port Isabel has been fighting every step of the project. The city is worried about air pollution and fires. It is concerned about interference with shrimpers’ livelihoods, and certain that a big plant will drive away tourists. And then there is the risk of explosion.
“A facility like this threatens our way of life,” Hockema said.
PHMSA has approved the safety plans for three proposed LNG export terminals along the Brownsville Ship Channel, though other regulatory hurdles remain. One was canceled this year when its developer, Annova, decided that the faltering export market wouldn’t justify the investment. The remaining two, Texas LNG and Rio Grande LNG, would abut each other on the Brownsville Ship Channel.
During the permit process, all three projects presented calculations regarding vapor cloud explosions based on small potential spills and the model that critics say lowballs the shock wave emanating from a blast. A spokeswoman for Texas LNG, Camilla Siazon, said the company would have no comment and referred questions about explosion hazards to federal regulators.
Hockema said he fears that the Texas LNG terminal will be approved and built, and then abandoned for lack of business, leaving the town with a permanent, hulking eyesore. That would be unfortunate for his city, but not as unfortunate as the detonation of dozens of tons of volatile hydrocarbons.