SoCalGas believes that this was an "off-gassing" of the soil, which has happened at the site before.
There are possible new concerns for Porter Ranch residents near the Aliso Canyon underground gas field Monday as methane was detected seeping out of soil near a gas well plugged earlier this year following a four-month leak.
SoCalGas inspectors, using infra-red camera technology, detected "a very slight and intermittent observation of methane" at the SS-25 wellhead of the Aliso Canyon Storage Facility at 7:45 a.m. Saturday, spokesman Sergio Jimenez told City News Service.
"We believe this is a continuation of off-gassing from the soil that has previously been observed at the site," Jimenez said. "This recent off- gassing of the soil coincides with the recent intense rain events at the site and is not believed to pose a present or potential hazard to human health, safety or the environment."
SoCalGas continues to monitor the site, he said. "No anomalies have been detected through other monitoring techniques, including the fenceline monitoring system and visual inspections, and there is no discernible odor at the site."
The earlier leak, which emitted 109,000 metric tons of methane and displaced at least 7,000 Porter Ranch area residents, was detected on Oct. 23, 2015.
That leak at the 3,600-acre underground storage facility was not capped until early February. Scientists said it was the largest methane leak in U.S. history.
SoCalGas has requested state approval to resume natural gas injections at the site while neighbors and environmental activists want it shut down permanently.