Five hundred feet above the Central Valley, a line on Stephen Conley’s laptop screen jumped.
Conley peered over from the pilot seat of his single-engine plane. The line showed methane levels in the surrounding air as he flew downwind from a natural gas pipeline buried in the green hills below. A sharp spike could mean that the pipeline had sprung a leak, venting gas into the sky. Methane is the fuel’s main ingredient.
Conley studied the screen and shook his head. False alarm.
“That’s not the shape you’d want,” he said. The line, twitching as it updated every second or so, had leveled off into a plateau – probably just elevated background levels of the gas.
A few miles more, and it leapt again, sharper this time.
“Now, this could be interesting,” Conley said, glancing from the screen to the ground, dotted with grazing cattle. “Or maybe not. Could just be the cows.”
Conley, an atmospheric scientist, is part of a team at UC Davis that has developed a system to hunt pipeline leaks by plane. For utility companies, the benefits could be big.
Pacific Gas and Electric Co., which helped fund the project, operates roughly 6,000 miles of natural gas transmission lines. The deadly 2010 explosion of one of them, beneath San Bruno, forced the company to re-evaluate the safety of its entire network.
In the past, checking for leaks, particularly in California’s vast rural spaces, often meant flying over buried pipelines and looking for vegetation killed by escaping gas. It’s an imprecise method – especially in a state where most of the vegetation looks dead for half the year. Another approach uses lasers fired from hovering helicopters to detect methane. But helicopter flights are expensive.
Other potential uses
Conley and fellow UC Davis atmospheric scientist Ian Faloona developed their system with a $295,000 grant from PG&E and the Pipeline Research Council International, an energy-industry collaborative. That doesn’t cover the cost of the plane but does include the methane-sniffing equipment, bought off the shelf for around $50,000.
“Our No. 1 goal at PG&E is the safety of the public, so we’re always looking for ways to find and fix leaks in our pipelines, and we believe this technology can help,” said Kevin Armato, a manager of asset engineering at PG&E.
The technology has other potential uses as well.
The growing use of hydraulic fracturing, or fracking, to extract natural gas from shale has alarmed environmentalists, many of whom question whether the process releases too much methane into the atmosphere. Methane is a potent greenhouse gas, trapping heat much more effectively than carbon dioxide. Conley has already flown over fracking fields in Utah, where he found high methane levels, and Colorado, where he found very little.
“One of my thoughts was to just go across the country and see which fields are worth a serious look,” Conley said. “Does fracking have a particular profile, or does it vary from field to field? That’s the kind of thing we could look at.”
The system developed by Faloona and Conley sucks in air through a small plastic tube beneath the plane’s right wing. A small, portable spectrometer inside the plane uses light wavelengths to determine how much methane, carbon dioxide and water vapor the air contains.
Some locations difficult
A computer program developed by the UC Davis team displays the methane levels on one half of the laptop screen. The other half shows the plane’s location and heading, as well as the path of the nearest pipeline.
The system constantly monitors wind speed and direction, using that information to calculate the best route to fly when hunting for leaks. The route, downwind of the pipeline, shows on the computer screen as a series of yellow dots.
PG&E has already run the UC Davis system through several tests, intentionally releasing methane along pipelines and asking Conley to spot the plumes. It works, although finding leaks can be easier in some locations than others. One test was located near Rio Vista, in the Sacramento-San Joaquin River Delta, where methane from decaying plants regularly bubbles to the surface.
“It was so hard to see things there – so messy,” Conley said.
Conley and Faloona are still fine-tuning the system but want to make it available for other people to customize and tweak.
“The idea is that it’s a technology that anyone can take and improve on,” Faloona said. “We have this great opportunity to do a service that can do real good for the industry and for the environment.”
David R. Baker is a San Francisco Chronicle staff writer. E-mail: firstname.lastname@example.org