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Meetings & Hearings

Landfill Methane Emissions, Chapter 173-408 WAC

Public hearing — online

Dec. 6, 2023, 10 a.m., online webinar

We are holding a public hearing about the rulemaking for 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 will implement new requirements:

  • Technology and performance requirements
    • Gas collection and control system installation
    • Gas collection and control system design plan
    • Gas control system equipment requirements
    • Gas collection and control system performance requirements
    • Methane destruction efficiency requirements for flares and energy recovery control devices
    • Requirements for open flare systems
    • Requirements for landfill gas treatment and processing
    • Wellhead gauge pressure requirements
    • Requirements for devices measuring gauge pressure
    • Requirements for instruments used to measure methane
    • Control device destruction efficiency calculation requirements
    • Gas generation flow rate calculation requirements
    • Source testing requirements for any gas control device or devices
  • Monitoring requirements
    • Instantaneous and integrated surface emissions monitoring
    • Surface monitoring design plan
    • Remonitoring and corrective action(s) for methane limit exceedances 
    • Gas collection and control system component monitoring
    • Methane leak rate limits for treatment systems that process routed gas
    • Wellhead gauge pressure monitoring
    • Shutdown and removal of the gas collection and control system
  • Reporting and recordkeeping requirements
    • Waste in place reporting
    • Landfill gas heat input capacity calculation and reporting
    • Surface emissions monitoring reporting
    • Gas collection and control system operations reporting
    • Records maintenance for monitoring, source testing, landfill operations, operation of the gas collection and control system, methane level exceedances, and actions involving the disturbance or removal of areas of the landfill surface
    • Reporting for capping of landfill gas collection wells, removal or cessation of gas collection and control system equipment
    • Landfill closure reporting to Ecology or the local clean air agency
  • Other requirements
    • New statutory civil penalties for violation of the law and implementing rules
    • Maximum methane concentration limits for both owners and operators of active and closed municipal solid waste landfills
    • Exemptions for methane concentration limit exceedances due to activities defined in RCW 70A.540.050(3)
    • Method for landfills to claim exemption from the rule
    • Alternative compliance measures
    • Terms and definitions

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 municipal solid waste landfills, as defined in RCW 70A.540.010. The proposed rule exempts the following types of landfills from these new requirements:

  • Landfills that receive or received only hazardous waste(s)
  • Landfills regulated under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA, also known as Superfund), if they meet the criteria for exemption set forth in the rule
  • Landfills that receive or received “only inert waste or non-decomposable wastes,” as defined in WAC 173‑350‑100
  • Limited purpose landfills, as defined in WAC 173-350-100


We write rules to implement and enforce state and federal environmental laws and rules.  Ecology follows a three-phase process for rulemaking:

  1. Announcement and development
  2. Proposal
  3. Adoption

For each phase of the process, we update the rulemaking web page and notify interested parties. We also file notice in the Washington State Register. To learn more about Ecology’s rulemaking process, read the Frequently Asked Questions.

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Dec. 6, 2023, 10 a.m.
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Bill Flagg
Rulemaking Lead
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Comment period

Landfill Methane Emissions, Chapter 173-408 WAC — Proposed rulemaking
Closes: Dec. 13, 2023, 11:59 p.m.
See details

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