Chapter 173-408 WAC

Ecology proposes a new rule Chapter 173-408 WAC, Landfill Methane Emissions. The purpose of this rulemaking is to implement Chapter 70A.540 RCW, Landfills – Methane Emissions.

This rulemaking may consider:

  • Reporting requirements
    • Establish a method for landfills to claim exemption from the rule.
    • Waste in place reporting requirements.
    • Landfill gas heat input capacity calculation and reporting requirements.
    • Records maintenance and reporting requirements related to monitoring, testing, landfill operations, operation of the gas control device, gas collection system, and gas control system.
    • Reporting requirements for capping of landfill gas collection wells, removal or cessation of gas collection and control system equipment.
    • Landfill closure reporting requirements.
  • Monitoring requirements
    • Instantaneous and integrated surface monitoring requirements.
    • Methane concentration limit requirements determined by instantaneous or integrated surface emissions monitoring.
    • Exemptions for methane concentration limit exceedances due to activities defined in RCW 70A.540.050(3).
    • Gas control system monitoring requirements.
    • Methane leak rate limits for treatment systems that process routed gas.
    • Wellhead gauge pressure monitoring requirements.
  • Technology requirements
    • Gas collection and control system installation requirements.
    • Gas collection and control system efficiency requirements.
    • Gas collection and control system landfill gas leak limits.
    • Methane destruction efficiency requirements for flares and energy recovery control devices.
    • Requirements for gas collection and control systems that use an open flare.
    • Requirements for devices measuring gauge pressure.
    • Requirements for instruments used to measure methane.
    • Landfill gas control system equipment requirements.
    • Control device destruction efficiency calculation requirements.
    • Source testing requirements for any gas control device or devices.
  • Other
    • Civil penalties for violation of the law and implementing rules.
    • Terms and definitions.

As stated by RCW 70A.540.020(3), this rulemaking must be informed by landfill methane regulations adopted by California Air Resources Board, Oregon Environmental Quality Commission, and EPA.

This rulemaking applies to owners and operators of municipal solid waste landfills that received solid waste after January 1, 1992. This includes both active and closed landfills. Landfills that are exempt from these new requirements are:

  • Landfills that receive only hazardous waste, or are currently regulated under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA, federal Superfund law).
  • Landfills that receive only inert waste or non-decomposable wastes.

Rulemaking timeline


Announcement phase (CR-101)

Filing date:
Dec. 8, 2022

Announcement documents

Rule development phase

December 8, 2022 – Fall 2023

Public input & involvement

Ecology plans to hold stakeholder meetings in Spring 2023. We will update this page with meeting specifics. To get updates about these meetings and this rulemaking, join our email list.

Additional languages

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