California AB 28 Becomes Law: What Landfill Operators Need to Prepare for

• AB 28, now Chapter 356 of the 2026 statutes, establishes a statewide framework for identifying and responding to subsurface elevated temperature events, generally involving temperatures persistently exceed 131°F over a substantial area and additional performance criteria established by CalRecycle
• The law shifts elevated temperature management toward earlier detection, documented investigation and coordinated corrective action
• AB 28 takes effect January 1, 2027, giving operators time to assess monitoring coverage, data quality and response plans before the new requirements take effect

Heat generation is normal within municipal solid waste landfills. But abnormal reactions can push temperatures beyond typical operating conditions and affect landfill gas composition, odors, settlement and leachate management. The U.S. Environmental Protection Agency identifies temperatures above 131°F as a common indicator of an elevated temperature landfill and notes that these conditions can increase facility management costs.

California Assembly Bill 28 was signed into law by Governor Gavin Newsom on September 20, 2026 and chaptered as Chapter 356, Statutes of 2026. The law establishes a more defined framework for responding to subsurface elevated temperature events at certain solid waste landfills and gives CalRecycle additional authority to require notification, data reporting, mitigation measures and corrective action when qualifying events occur.

Under the law, a subsurface elevated temperature event occurs when subsurface gas or waste temperatures persistently exceed 131°F over a substantial area and meet other performance criteria determined by CalRecycle.

If an event occurs, the landfill owner or operator will be required to notify CalRecycle and other specified state and local agencies, provide temperature data when requested and take actions CalRecycle deems necessary to mitigate and resolve the event. Those actions could include development of a corrective action plan.

Failure to comply with the notification, data-reporting, mitigation or corrective-action requirements can result in administrative civil penalties of up to $100,000 per day. For penalties imposed under those provisions, penalties do not begin accruing until the 31st day after CalRecycle issues a notice of violation. The law separately authorizes penalties of up to $100,000 per day for violations of its multiagency-response and air-monitoring provisions.

The owner and operator must reimburse participating agencies and the local health department monthly for reasonable and necessary staffing, overhead and other costs associated with the multiagency response.

The framework also creates a pathway for coordinated air monitoring, public health assessment and multiagency response when an elevated temperature event affects surrounding communities.

AB 28 takes effect January 1, 2027. The law also authorizes CalRecycle to adopt emergency regulations to implement and enforce the new provisions. For operators, the focus can now move from tracking the bill’s progress to evaluating how current monitoring, escalation and response processes align with the new framework.

With the law in place, the real question is whether operators can identify a developing temperature trend early, interpret the data with confidence and take clear, well-documented action.

Operators should evaluate:

• Whether existing landfill gas monitoring provides sufficient visibility into temperature trends
• How quickly abnormal readings are identified, validated and escalated
• Whether monitoring, gas composition, settlement, leachate and other site information can be reviewed together
• How corrective action responsibilities, agency communication and documentation would work during an event

A stronger monitoring and response program can give operators more time to investigate changing conditions, make informed decisions and demonstrate a clear record of action.