A HELICOPTER equipped with laser gas detection equipment made numerous low-altitude passes over the Monterey Peninsula last weekend, prompting complaints about its noise and quite a few different theories about what it was up to — everything from searching for drug smugglers for the DEA, to conducting mapping surveillance for the NPS.

The mission of the helicopter turned out to be something never seen before in these parts: It was searching for possible leaks from gas mains through the Monterey Peninsula.

“We are flying for PG&E, doing leak surveys on their pipelines,” said Winston Johnson, CEO of Lasen Technology of Las .Cruces, NM. “We’ll be flying over 25,000 miles of pipe, which includes most of the high-pressure lines PG&E has in California.”

The utility stepped up leak detection after the San Bruno disaster in September 2010, when a high-pressure gas main through a residential neighborhood exploded, killing eight people and destroying 38 homes.

“They’re being very proactive about leak detection, and we’re helping them do that,” said Johnson.

His company’s helicopter is equipped with a laser tuned to the frequency of methane gas, he said. As the helicopter flies over the route of a gas main, the laser, mounted on the helicopter’s belly, bounces back from the terrain below but is partially absorbed if it encounters even very low levels of methane. The reflected laser is picked up and measured by sensors on the helicopter and matched with GPS data, producing a map of any possible leaks.

“Using helicopters is just another tool in our toolbox to identify any leaks and make repairs as quickly as possible,” said PG&E spokesman Monica Tell.

She said the company’s pipeline network includes everything in the state from Bakersfield to the Oregon border, and that surveys would be made throughout the network six times a year. The helicopter did not detect any leaks last weekend, but will be back over the Monterey Peninsula in December, she said.

Concern about the chopper was heightened because it was flying just a few hundred feet above the ground, but the low altitude is necessary for the laser detection equipment to work.
“We don’t fly higher than 500 feet,” Johnson said.

Even at that low altitude, the laser is safe for people on the ground, according to Johan Wictor, who is with Pergam Technical Services, which also does helicopter gas leak detection for many of the nation’s largest gas companies.

“You can not see the laser, and it does not burn you,” he said.

His company also records visual images of pipeline routes, which allows companies to keep an eye out for erosion, poachers and other problems that could affect pipeline safety. ÅAnd, despite the occasional noise complaint, “when we tell them what we are doing, most people are comfortable with that,” Johnson said.

According to Tell, the helicopter laser detection is so sensitive, it will help keep gas leaks from becoming dangerous, as the one in San Bruno did.

“We can pick up concentrations as low of five parts per million,” Johnson said.

Natural gas isn’t considered explosive unless it is     at least 5,000 ppm in an enclosed space, according to Prasad Saurabh, a professor of epidemiology and community health at the University of Ottawa.
The equipment is so sensitive, it also picks up other sources of methane. “If we fly over a farm, I can assure you the laser is going to see the cows,” Johnson said.

To see a map of local gas mains, go to http://www.pge.com/myhome/edusafety/systemworks/gas/transmissionpipelines/