Report Shows Porter Ranch Gas Leak the Biggest in US History


A report in the journal Science shows that the months-long natural gas leak from a well in California’s San Fernando Valley released 97,100 metric tons of methane and 7,300 metric tons of ethane into the air above Los Angeles, researchers estimate. For the first six weeks of the leak, the well spewed at most 59 metric tons of methane and 4.4 metric tons of ethane per hour — twice the normal emission rate of the entire Los Angeles Basin, the researchers say.

For the first six weeks of the leak, the well spewed at most 59 metric tons of methane and 4.4 metric tons of methane per hour — twice the normal emission rate of the entire Los Angeles Basin, the researchers say.

The leak began in October in one of the wells at the Aliso Canyon oil storage facility. After many attempts to plug the leaky pipe, workers finally sealed it on February 18.

To assess the impact of the leak on local air quality, Stephen Conley of the University of California-Davis and his colleagues assessed the impact of the leak collected downwind air samples on the ground and from above — via 13 flights aboard a small aircraft over three months of the leak.

Methane and ethane both increase atmospheric ozone levels and, at high levels, impact human health.

Los Angeles is home to many small natural gas leaks as well, another group reports February 20 in the Journal of Geophysical Research: Atmospheres. Mapping methane release across the basin prior to the blowout revealed 213 hotspots of unknown origin. Such maps could also give researchers a clearer sense of the impact of the blowout on Los Angeles methane emissions.

Meantime, the Superior Court granted the Los Angeles County Board of Supervisors’ request to extend the period for returning home for those residents who chose to relocate as a result of the Aliso Canyon natural gas leak.

SoCalGas issued a statement saying: “Throughout this difficult time, SoCalGas has been committed to providing appropriate relocation assistance to affected residents until independent data indicated that relocation was no longer necessary.”

The statement went on to say: “The Division of Oil, Gas & Geothermal Resources (DOGGR) determined last week that the leak has been permanently stopped, and weeks of air-quality monitoring data and scientific analysis from independent air and health agencies – including the Los Angeles Department of Public Health, CalEPA’s Office of Environmental Health Hazard Assessment, California Air Resources Board and South Coast Air Quality Management District – demonstrate there is no environmental or health reason for any further delay in enabling residents to return home.”