Workers at the Simi Valley Landfill pumped liquid nitrogen into layers of buried trash Tuesday, hoping to quench a smoldering underground fire.
Somewhere about 40 feet beneath the landfill's surface, the heat of rotting trash ignited a stubborn fire last week that could have spread and worsened if landfill operators had not acted in time to stop it, said Terry Gilday, a county environmental official.
While landfill officials estimate the burning area is up to 9 feet across and 10 feet deep, Gilday said it could be as much as 100 feet in diameter.
"It's a very large nuisance at this point," said Gilday, solid waste manager for the Ventura County Department of Environmental Health. "If left untended, [the fire] could become a very serious problem. It could extend through larger and larger sections of the landfill and start contributing to air pollution."
Landfill workers noticed the fire for the first time last week, spotting a plume of smoke rising from the layer of dirt that is plowed over each layer of trash at day's end, said Dan Vidal, the landfill's general manager.
Workers capped an acre above the fire with a layer of wet clay one to three feet thick, hoping to cut off any air that might be feeding the flames, said Vidal.
They also shoved long metal thermometer tubes down through the landfill to measure the fire's temperature, he said.
Then late Monday night, workers began pumping the first of 300,000 gallons of liquid nitrogen down through the tubes, which should snuff out any remaining flames, Vidal said. But until the nitrogen--which starts out frozen at sub-zero temperature--warms up to ambient temperature, it will be difficult to read the thermal probes and accurately gauge the fire, he said.
"These fires behave very peculiarly," Gilday said. "They'll run up against something in the ground we may not even know is there and just go out.
"On the other hand," he said, "It may weave a serpent's path through the fill material, burning here and not burning there . . . . That's one of the things that makes an underground fire so dangerous."