A natural gas leak alert near the assisted living community at 2431 Mariner Square Dr. was lifted Wednesday evening after PG&E workers secured a leaking relief valve, according to an Alameda fire Department news bulletin. Nearby residents had been told to "shelter in place" and remain indoors.
The leak was reported at 5:08 p.m., an Alameda Fire Department dispatcher said.
According to the AFD bulletin, a large (about 4-inch) natural gas relief valve was off-gassing.
A PG&E spokesman said Wednesday night that the problem was caused by a generator at a cogeneration plant that is supplied with natural gas by PG&E. When the generator shut off, natural gas was sent back through PG&E lines. That triggered the relief valve to release the excess gas, the spokesman said.
"It's set up as a safety precaution," he said. "Everything worked as it is supposed to."
He said PG&E workers arrived on scene at 5:44 p.m. All excess gas had already been released by that time, he said.
The spokesman could not immediately identify the cogeneration plant where the problem originated. According to the California Cogeneration Council, cogeneration plants are operated by mainly by private businesses and use natural gas to generate both electricity and thermal energy.
Many Alameda residents were notified of the leak by via the city's CodeRED phone system.
Although the problem was reported to the Alameda Fire Department at 5:08 p.m. and to PG&E at 5:16 p.m., several local residents told Alameda Patch that they received their CodeRED "shelter in place" calls around 6 p.m.