LOS ANGELES — Three years ago, environmental regulators discovered garbage burning deep inside the Chiquita Canyon Landfill in the Santa Clarita Valley. Few imagined the calamity that would follow.

Somehow the landfill’s pollution control system introduced oxygen below, causing decades-old waste to rapidly decompose, generating intense heat and eventually widespread smoldering, federal and state environmental agencies say. The broiling temperatures released toxic gases and hazardous liquid waste that bubbled up to the surface. Residents living in the nearby communities of Val Verde and Castaic have phoned in thousands of complaints about stench and lived with nausea, dizziness and trouble breathing.

The underground fire has tripled in size since first confirmed in 2023. Recently a towering mound of landfill garbage perched on the hillside has warped and threatens to trigger an avalanche of garbage and chemical-filled liquid, or leachate, according to the California water board. Waste Connections, the landfill’s owner and operator, says it has been working to stabilize that area.

“In a worst case scenario, the hillside can liquefy and actually slide into the community,” Assembly member Pilar Schiavo, D-Santa Clarita, said at a news conference last month.

At first, local officials described the problem in Los Angeles County at Chiquita Canyon landfill as a rare, even unprecedented disaster. But since then, California regulators have learned that at least two other landfills are wrestling with high temperatures and similar conditions.

Scorching temperatures have overtaken at least 30 acres of El Sobrante landfill near Corona in Riverside County. Excessive heat and emissions have also been detected at Avenal landfill in the San Joaquin Valley.

The discoveries raise an unsettling question: How many landfills are dealing with these disasters? Are they a broader problem in California?

At Chiquita Canyon, conditions have continued to deteriorate.

In the years that I’ve covered this issue, I’ve met residents who’ve taken extreme measures to escape the toxic pollution. They’ve worn gas masks and slept overnight in grocery store parking lots. Several families sold their homes.

Those who have stayed continue to deal with risks to their health and safety. Schiavo said the stench near Chiquita Canyon has gotten worse in recent days as workers try to stabilize the hillside.

In Val Verde, children out of school for the summer have hardly been able to enjoy their time off.

“They are already suffering — prisoners in their own homes,” Schiavo said. “They have a great trampoline in front of their house. They can’t jump around on because of this toxic air.”

On a recent weekday morning, landfill workers were staged around the damaged, western side of the landfill with heavy machinery. Across the street, dozens Los Angeles County firefighter recruits jogged at the Del Valle Regional Training Center, pushing through the inescapable aroma of trash in the air.

Abigail DeSesa, a longtime resident of Val Verde who lives about a mile from Chiquita Canyon, said she regularly wakes up with pounding headaches she believes are related to landfill gases from the fire. She’s gone to a community relief center set up at a local hotel to escape the smell, but has to return home at the end of the day.

“The gas is getting into our homes and I am waking up sick every morning,” DeSesa said. “Where is the relief for that? I did not break the landfill, so why am I paying a heavy price with my physical and mental health to fix it?”

Chiquita Canyon closed at the end of the 2024 and stopped accepting new garbage. But the fire is expected to last for years as it continues to consume decades-old trash.

Underground landfill fires are complex, nearly impossible to extinguish once they break out. As regulators search for a solution, residents are really struggling with the wait.

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