California’s Updated Landfill Methane Regulation: Key Changes & How Landfill Operators Can Prepare

Why California Updated the Landfill Methane Regulation

CARB approved amendments to the LMR in November 2025, updating a regulation originally adopted in 2010. With methane recognized as a greenhouse gas, the updated regulation strengthens monitoring requirements, expands expectations, and incorporates remote sensing and alternative-monitoring technologies for methane detection and LFG management.

The revised regulation reflects several developments within the solid waste industry, including:

Who Must Comply with the Updated LMR?

The updated LMR applies to California’s 188 MSW landfills that accepted waste after January 1, 1977, and exceed the 450,000-ton waste-in-place exemption threshold. Both active and closed landfills remain subject to the regulation because methane generation can continue for decades after landfill closure.

Key Changes to California’s Landfill Methane Regulation

The amendments affect wellhead monitoring, GCCS downtime, surface emissions monitoring, remote-sensing response, corrective actions, design plans, and qualifying closed landfill operations.

Expanded Wellhead Monitoring Requirements

The updated regulation expands monthly wellhead monitoring requirements to include:

• Methane (CH₄)
• Carbon dioxide (CO₂)
• Oxygen (O₂)
• Temperature
• Vacuum
• Flow rate

Liquid‑level monitoring has been reduced to once per year, while follow-up monitoring is now required after corrective actions are completed.

Impact: Operators will need expanded field monitoring capabilities, upgraded instruments, improved data management practices, and more structured wellfield oversight.

Removal of Fixed Downtime Allowances

The previous 120-hour and 240-hour downtime allowances have been eliminated.

Under the updated regulation:

Impact: Operators should prepare mitigation strategies before planned shutdowns occur and maintain documentation that explains operational decisions.

Modernized Surface Emissions Monitoring

Quarterly surface emissions monitoring (SEM) remains a core compliance requirement. However, the updated regulation establishes a process for using alternative monitoring technologies, including:

The amendments also connect SEM follow-up activities with remotely detected methane plume response requirements.

Impact: Operators should assess whether approved alternative technologies can improve monitoring coverage or field efficiency while maintaining procedures for responding to methane plume observations identified through external monitoring programs.

Remote Sensing & Satellite Response Requirements

The updated regulation adds response requirements for methane plumes detected through satellite and other remote-sensing programs.

Operators must now:

Impact: Facilities operating within existing compliance limits may need to investigate and document methane plumes identified through remote monitoring programs.

Strengthened Corrective Action Requirements

The updated LMR establishes a more structured corrective action process that includes:

Impact: Operators must document investigations, complete verification monitoring, track recurring problem areas, and demonstrate that corrective actions resolved the identified condition.

Expanded GCCS Design Plan Requirements

GCCS design plans must now address:

Impact: Design plans will require ongoing review and updates as conditions and operational requirements change, rather than serving solely as initial engineering documents.

Updated Requirements for Closed & Declining LFG Landfills

The updated regulation introduces flexibility for qualifying closed landfills by allowing:

Impact: These provisions provide operational flexibility without eliminating monitoring, documentation, or regulatory compliance.

How Landfill Operators Can Prepare for the Updated LMR

Although the updated regulation becomes effective January 1, 2027, landfill operators should prepare well before the compliance date. Early planning provides time to evaluate existing landfill gas systems, update operating procedures, and identify potential compliance gaps before the new requirements take effect.

Early planning can reduce operational disruptions and give operators time to address equipment, staffing, and data-management gaps. Noncompliance may result in notices of violation (NOVs), monetary penalties, and other enforcement action.

Operators should evaluate existing monitoring programs, maintenance practices, documentation procedures, and LFG system operations to determine whether changes will be needed before the regulation becomes effective.

Evaluate Monitoring Capabilities

Expanded monitoring requirements may require updates to equipment, staffing, and data management practices.

Operators should consider:

Review Maintenance Planning

The removal of fixed downtime allowances places greater emphasis on preventive maintenance and operational planning.

Operators should:

Modernize SEM Programs

Facilities should evaluate whether current monitoring programs support the flexibility introduced under the updated regulation.

Operators should assess:

Update GCCS Design Plans

GCCS design plans should be reviewed to determine whether they address the additional information required under the updated regulation.

Areas for review include:

Strengthen Documentation & Reporting

The updated LMR places greater emphasis on documentation throughout monitoring, maintenance, and corrective action activities.

Operators should consider:

Consistent documentation demonstrates compliance and gives operators information that can improve LFG management.

How APTIM Supports California Landfill Operators

The updated LMR expands expectations for LFG monitoring, regulatory documentation, and operational performance. Meeting these requirements requires coordinated planning across engineering, operations, environmental compliance, and LFG management programs.

APTIM works with California landfill operators to assess regulatory readiness and implement site-specific changes through solid waste services, landfill gas construction, environmental compliance, and operational services. Our services include:

• LMR compliance gap assessments
• LFG monitoring program evaluations
• GCCS design & optimization
• SEM program planning & implementation
• Satellite methane plume response planning
• LFG operations & maintenance
• Environmental compliance & reporting
• Staff training & operational procedure development

APTIM integrates engineering design, field monitoring, LFG operations, and environmental compliance expertise to help landfill operators address regulatory requirements while improving system performance and operational coordination.

Connect with APTIM’s solid waste and landfill gas specialists to assess LMR readiness, identify monitoring and documentation gaps, and develop a site-specific compliance plan before the updated requirements take effect.

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Published September 2026