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Aliso Canyon Methane Leak Was Worst in Recorded History, Study Finds

Aliso Canyon Methane Leak Was Worst in Recorded History, Study Finds

An aerial view showing the SS-25 wellheads at Aliso Canyon. Credit: Wikimedia Commons

After analysing samples directly obtained from around the leak site, scientists found that the amount of methane released was equal to those emitted by mid-sized European countries in a year.

A map showing the relative locations of the Aliso Canyon storage facility and Porter Ranch. Source: Google Maps
A map showing the relative locations of the Aliso Canyon storage facility and Porter Ranch. Source: Google Maps

From October 2015 to February 2016, a processed natural gas storage facility in California leaked significant amounts of greenhouse gases and diffused carcinogenic substances into the surrounding San Fernando Valley, and ended up being one of the largest methane leaks in recorded US history. The processed gases included methane and ethane, both infamously implicated in eating away at the planet’s ozone layer, as well as sulphur-containing compounds added as odourants and linked to many respiratory illnesses.

Though a measure of control was imposed at the site of the leak – the SS-25 well at the Aliso Canyon storage facility – in early December 2015, Bloomberg reported that people living in the extended neighbourhood of the facility had realised a complete stoppage wouldn’t happen by the end of the year. Before the leak had begun, the facility had been topped up with 86 billion standard cubic feet (SCF) of gas in time for winter demand. How much would leave, and what impact would it have?

Between November 7, 2015, and February 13, 2016, a group of American scientists flew a small plane fitted with a sampling system through the gas plumes over Aliso Canyon and around the area to get a sense of the numbers. The results of their analyses were published in the journal Science on February 25. They write in the paper that in “the post-COP21 world, rapid evaluation of episodic releases of GHGs like the Aliso Canyon blowout will be an essential contribution” to meeting the climate agreement’s accountability requirements.

In the 118 days that the leak lasted for, 5 billion SCF of methane and 375.9 million SCF of ethane had been released. The total emissions amounted to only 3% of Aliso Canyon’s capacity but the result, according to the scientists, was the second-largest methane leak in recorded American history. This is very bad news because methane is much more potent as a greenhouse gas than carbon dioxide – upto 84 times for the first 20 years it’s in the atmosphere.

The leak also highlighted a host of problems about how authorities deal with such ‘fugitive emissions’ – including the fact that data on them isn’t readily available and that scientists had to fly a plane through the plumes to calculate their estimates. Methane in particular complicates matters because, apart from its greater potency relative to carbon dioxide, it is hard to detect (being colourless and odourless) and also dissipates quickly. And without stringent checks every step of the way, from its production to consumption, we’re likely to err on the side of solace about how much of the gas is in use at any time.

In fact, on February 24, the Environmental Protection Agency announced just this: that officials had underestimated the amount of methane released into the atmosphere by the US in 2013 by 27%. This ‘deviation’ stands in stark contrast to the need for increasingly accurate climate calculi, and requires law- and policy-makers to draw up regulations that are able to account for such overshoots. So, in those 118 days the Aliso Canyon blowout lasted, engineers had tried at least seven times to plug the leak, and the magnitude of the numbers only underscores the importance of each attempt.

Time series of the Aliso Canyon natural gas leak. Credit: DOI: 10.1126/science.aaf2348
Time series of the Aliso Canyon natural gas leak. Credit: DOI: 10.1126/science.aaf2348

The first one was a typical response: pouring a briny liquid down the shaft to suppress the rising gas. After that failed, it was found that the gas wasn’t leaking from a rupture near the surface but one beneath 500 feet of soil. Once that spot was accessed, on November 13, brine was again poured down. This time, however, the liquid was slapped out of the way by a sudden upwelling of the gas and formed a column in the surrounding earth that made it easier for the rest of the gas to escape. The leak was finally plugged on February 18 by accessing the rupture through another specially dug tunnel and pouring in liquids reinforced with cement.

Aliso Canyon gas plume transport into populated areas. Credit: DOI: 10.1126/science.aaf2348
Aliso Canyon gas plume transport into populated areas. The white line is the flight path. Credit: DOI: 10.1126/science.aaf2348

However, by December 23, data collected by the airplane showed that “exceptionally high concentrations” of methane and ethane had been carried to the San Fernando Valley a few kilometres to the south of Aliso Canyon. Since the two months until then, news reports had emerged of the valley’s residents, especially from the wealthy Porter Ranch neighbourhood, smelling a faint but pungent odour – of the sulphur-containing mercaptan compounds added to the otherwise odourless gas, and complained of headache, nausea, nosebleeds and dizziness.

Smaller concentrations of butanes and pentanes, the so-called higher hydrocarbons, from the emissions also started to condense on surfaces around the area and form oily patinas. Finally, the presence of trace amounts of cancer-causing benzene were also reported in the study.

Credit: DOI: 10.1126/science.aaf2348
Credit: DOI: 10.1126/science.aaf2348

The residents had started to gather in Porter Ranch’s public spaces to protest the leak and demand that state authorities hold the Southern California Gas Company, operator of Aliso Canyon and a division of Sempra Energy, accountable. The principal issue was that SoCalGas had removed a safety valve in the problematic well in 1979 and then not replaced it because it wasn’t legally obligated to, turning some commentators to remark that the law had failed to motivate private corporations to look beyond their profits, and that privately operated energy infrastructure be declared a part of the commons. Environmental activist Erin Brockovich, present at the public gatherings, called the leak the worst such disaster since the BP oil spill in 2010; justifiably alarming metaphors, such as likening the leak to a ‘volcanic eruption‘, entrenched themselves in popular narratives of the accident. Had the valve been replaced, the leak could’ve been fixed within weeks instead of months.

The only other larger methane leak was the Moss Bluff incident in 2004, when 6 billion SCF of gas escaped from the Texan facility. However, a subsequent explosion and fire burnt most of the methane to form carbon dioxide, which is far less potent as a greenhouse gas. In this sense, the authors of the study write, “The total release from Aliso Canyon will substantially impact the State of California greenhouse gas emission targets for the year and is equivalent to the annual energy sector [methane] emissions from medium-sized [European] nations”.

The study’s conclusions provide a quantitative basis for bolstering legal action against SoCalGas, but that such actions will be taken at all was a given by early January for at least three reasons.

While California law is uniquely equipped among all American states to hold SoCalGas responsible for the leak’s impact on the climate, the emissions trading system through which it’s enforced doesn’t include subsurface leaks from corroded pipes in the shortlist of non-combustion sources for which operators are liable. As Sarah Duffy, a policy fellow at the University of California, Los Angeles, law school writes, “records of the cap-and-trade system will not give any indication that this leak occurred. That is worrisome.” This loophole must be fixed.

Second: California’s governor Jerry Brown had to declare an emergency on January 6, 2016, after paying a visit to the San Fernando Valley as well as under pressure from activists alleging complacency. The declaration forbade SoCalGas from injecting more gas into Aliso Canyon (from the 115 wells connected to it), transporting as much gas it contained as possible to other storage facilities, and required the company to arrange for independent air-quality tests around the SS-25 site.

But the most powerful motivation of all is that the leak occurred close to an affluent and influential community, that of Porter Ranch (where many homes cost $1 million). As a result, damages claimed (in at least 25 lawsuits) could run into the billions of dollars. Already, the company has decided to challenge a court order in the last week of February – that it must pay for relocating over 3,000 families for 30 days until it can say for sure that the leak’s been sealed off fully – on the basis of it incurring costs of $1.8-2.2 million each day.

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