Air quality regulators have ordered a private landfill in Castaic to take immediate steps to reduce a putrid odor that has prompted more than a thousand complaints from nearby residents.

On Tuesday, the South Coast Air Quality Management District sent an “order of abatement” to the owners of the Chiquita Canyon Landfill, which is located just south of the Val Verde community and west of Six Flags Magic Mountain.

South Coast AQMD says the agency began receiving a large number of odor complaints in May.

Investigators determined the stench was the result of elevated levels of sulfur, specifically dimethyl sulfide, in landfill gas emissions which “its gas treatment system is not designed to remove,” officials said.

Chiquita Canyon Landfill
Chiquita Canyon Landfill in Castaic, California. Aug. 16, 2023 (KTLA)

Since the start of the investigation, South Coast AQMD has received more than 1,200 complaints, the agency said in a statement.

“It has definitely increased,” Val Verde resident Alex Martinez told KTLA on Wednesday. “There were times when I could smell it, but it was more like a [normal] dump smell. Now, it has become a masking smell … a chemical smell.”

Since May, regulators have served the landfill with 42 notices accusing managers of violating health and safety codes. It is demanding Waste Connections Inc., the landfill’s parent company, take immediate steps to reduce the stench in the short and long terms.

On its website, Chiquita Canyon acknowledges the increased odor which, it says, is “due to an abnormal biotic or abiotic process” within the landfill waste mass.

Chiquita Canyon Landfill
Chiquita Canyon Landfill in Castaic, California. Aug. 16, 2023 (KTLA)

“This reaction is producing higher than normal levels of dimethyl sulfide (DMS) as well as leachate. DMS is produced when plant matter decomposes,” managers said.

The landfill outlines a number of steps managers say they are taking to mitigate the stench – among them, using fans and “odor neutralizer” misting systems.

Chiquita is also offering nearby residents air filtration devices.

A South Coast AQMD hearing is tentatively scheduled for Sept. 6.