Sunday, February 7, 2016

UC Davis pilot flies into gas plume to monitor Los Angeles methane leak

Pilot and UC Davis atmospheric scientist Stephen Conley flies toward the Aliso Canyon natural gas storage facility to measure the methane emissions from a leak.



Once a week since the beginning of November, when skies are clear with northern winds, Stephen Conley revs up a small, single-engine airplane and takes to the sky out of a hangar in Placer County.

The white and blue aircraft is equipped with a set of tubes along its underbelly and a backseat full of computing equipment but otherwise appears as an ordinary, albeit speedy, two-passenger plane.

It’s not until about two hours into his trek, over an area of Southern California, when Conley takes a turn toward the unusual: He switches to pollution-detection mode and begins sweeping the plane in and out of a giant, invisible plume of methane gas at gradually higher altitudes until the plane reaches the top.

His purpose is to monitor and measure the amount of methane coming from the Aliso Canyon natural gas leak, which started spewing methane-heavy natural gas in October, displacing thousands of residents from upscale, gated communities in the Porter Ranch neighborhood of northern Los Angeles. Gov. Jerry Brown has declared a state of emergency in the area for what is now being called the largest recorded leak of natural gas in California history.

State of emergency in place

The methane leak, first reported Oct. 23, has gradually slowed within the past few weeks. However, the state of emergency — with thousands displaced — remains in place as the gas company, SoCalGas, continues its attempt to plug the hole in the deep underground pipe suspected to be responsible for the leak.

Conley, a UC Davis atmospheric scientist and owner of the aerial survey company Scientific Aviation, was contracted for the flyovers by the California Energy Commission, which was looking to track the amount of greenhouse gas emissions expelled into the atmosphere by the leak.

Through his flyovers, Conley has recorded about 1,200 tons of leaked methane per day — equal to about 100,000 pounds per hour. To date, he estimates the leak has emitted 80,000 tons of methane — roughly equal to the weight of an aircraft carrier.

“The rate of methane we were seeing at the beginning ... was about equal to the total emissions of the entire Los Angeles basin at any given hour,” he said. “If you assume this leak will be stopped by March, then it will likely amount to 10 percent of California’s total methane emissions for the year. Just this leak on its own.”

Methane gas is flammable, and an additive in the natural gas gives it a rotten egg-like smell that some Porter Ranch residents complained made them nauseated or gave them headaches or nose bleeds. Authorities gave the residents a choice to evacuate or stay, and roughly 3,000 of them elected to leave.

Those who evacuated are allowed to return as they please, but officials say most have told them they will wait until the leak is plugged and methane and other gases have time to mix into the atmosphere and move out of the area.

The extent of the methane emissions wasn’t known until Conley took his first flight, two weeks after the start of the leak, to get a handle of its scale and impact.


Pilot and UC Davis atmospheric scientist Stephen Conley provided the first data on the methane gas leak in Los Angeles.


Value of air measurements

The energy commission solicited him for the first two flyovers, he said, because his plane was one of a few throughout the state capable of running such tests, and he was already working with the organization on a separate research project. He has subsequently conducted regular weekly flyovers for the California Air Resources Board, which took over the project from the energy commission with funding from SoCalGas.

Conley said taking measurements from the air is necessary because testing from the ground would be difficult, complex and time consuming.

“It’s rough terrain,” he said. “The well site is up in the hills. It’s difficult to get to where you need to be to take estimates.”

Conley’s plane pulls in the gas through the set of uptake tubes that test for gases such as carbon dioxide and methane. It measures the amount of each gas and the wind velocity at the time, and from that information he can calculate methane concentrations.

“We fly roughly 2 miles downwind of the leak site. We give the gas time to mix in the atmosphere before we grab it,” Conley said. “We fly into the plume, back out of it, climb up and then do it again. We climb up until we stop seeing the increase in the methane level. We can see all of this in real-time.”

Conley — who usually flies alone, but has brought an occasional guest — was the only scientist cleared to perform the mission initially, but said NASA’s Jet Propulsion Laboratory sent a specially equipped air vehicle into the plume last month to measure the gas.

Methane is a special concern as a greenhouse gas because it is about 25 times more powerful than carbon dioxide, said Dave Clegern, spokesman for the California Air Resources Board.

“We want to know how much has been emitted so we know how we can best deal with this once it is done,” he said.

And, Conley noted, a leak such as this is significant to people around the world, whether they realize it or not.

“This is not going to be some ‘L.A. getting hotter’ kind of problem,” he said. “This is a global issue. That total amount of gas (that he has measured so far) has already left L.A. It’s going out to the state, country and rest of the world and gets mixed into the global methane budget.”

Officials from SoCalGas have promised to fix the leak by March, saying it will take time to locate and plug the responsible pipe.

Seeking to prevent leaks

In Washington, California Sens. Barbara Boxer and Dianne Feinstein have written an amendment to an energy bill being considered in the Senate that calls for the Energy Department to review the situation and recommend any immediate steps the federal government might take to assist in solving the leak and in preventing and responding to future similar leaks.

Meanwhile, Conley said each additional flyover has found lower levels of methane, but there are not yet any plans to stop his flyover measurements until the leak is fixed.

And while he has enjoyed having a part in the project, he said the need remains for a formalized plan to respond to leaks like this in the future.

“For a country so concerned with greenhouse gas emissions, how can we not have something in place to measure these events when they do occur?” Conley said.

Story and photo gallery:  http://www.sfgate.com

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