A rare
chemical reaction deep within the landfill probably began in May 2022. The landfill's containment systems were overwhelmed with rainwater filtering through the rotting garbage. Oxygen may have intruded below the landfill cover causing the generation of extreme heat, production of excessive
leachate, and the buildup of pressure within a closed portion of the site. Hot, contaminated water has been forced to the surface, occasionally erupting like a
geyser. This leachate has changed the
landfill gas to have a nauseating, sulphuric odor, impacting thousands of nearby residents. The company has community
air quality monitoring stations in
Val Verde and in
Hasley Canyon Park in Castaic. While the residents of Val Verde have been smelling odors for many years, neighborhoods as far away as
Stevenson Ranch have complained to the
South Coast Air Quality Management District about the overwhelming stench. In 2024, the district received 13,000 odor complaints. A Community Relief Program by the company was instituted to provide funds to assist residents who want to relocate temporarily. The
Los Angeles Regional Water Quality Control Board denied permission to expand into an additional cell in late 2024, expressing concerns about the odors and the landfill's stability during a potential earthquake. After repeated enforcement actions and abatement orders had not brought actions resulting in sufficient reduction in the odors, the county of Los Angeles filed a lawsuit against the owners in December 2024. The landfill, which was accepting roughly 2 million tons () of solid waste annually, was closed to future waste disposal on
New Year's Day. The underground burn zone continued to grow, reaching an estimated by March 2025. ==References==