The nation's largest natural gas distribution utility, Sempra Energy's Southern California Gas Co. (SoCalGas), on Monday unveiled a series of methane detection sensors, following the completion of demonstration testing as part of a multi-billion-dollar pipeline safety enhancement program.

With timely state regulatory approvals, SoCalGas will begin wider deployment of the sensors, utility officials said. The current plan calls for installation of up to 2,000 sensors.

Part of SoCalGas' advanced meter communication system, the sensors detect natural gas leaks quickly near parts of the utility's 100,000-mile pipeline system spread over 20,000 square miles in the southern half of California.

SoCalGas installed 12 sensors at monitoring stations that are reading methane-in-air concentration levels at various locations throughout the Los Angeles Basin, providing readings every five minutes on gas levels near high-pressure transmission pipelines. "The sensors detect methane in the air and send an alarm within 15 minutes to a monitoring system," a utility spokesperson said.

"The sensors will detect natural gas at well below the limit that most people can by sense of smell, providing earlier detection of any unplanned gas escape incidents and more rapid dispatch of responders to investigate."

Solar-powered with supplementary batteries, the sensors have operated and performed as expected for nearly a year, according to SoCalGas. No excessive methane levels thus far have been detected. SoCalGas periodically tests and calibrates the sensors to confirm that they continue to operate correctly.

Each unit is contained in a small cabinet that can be attached either to an existing gas utility pole, wall, or other structure.

Despite being the nation's largest gas distribution utility system, SoCalGas officials contend their utility operations have one of the lowest methane emission rates in the nation while serving an area with 21 million people.

Commercially available methane sensors are being deployed, using nondispersive infrared sensor technology that has been in use for many years, according to the gas utility. Longer term, SoCalGas is not limited to the existing technology, the spokesperson said.

Improving methane detection capabilities is the focus of applying the utility advanced meter radio system to help record and transmit data from sensors stationed along the SoCalGas pipelines.

The broader safety enhancement program identifies pipeline segments through the SoCalGas system, scheduling them for pressure testing or replacement. Begun almost three years ago after the San Bruno pipeline rupture and explosion on a Pacific Gas and Electric Co. transmission pipeline, the safety enhancement effort includes upgrading, replacing and retrofitting hundreds of mainline valves with technology that allow for their remote opening and closing from a central control location or automatically in the event of a large pressure drop.