Chapter 173-408 WAC – Landfill Methane Emissions

On May 13, 2024, Ecology adopted 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 establishes new requirements for municipal solid waste landfills that received solid waste after January 1, 1992.

• Technology and performance requirements
  • Gas collection and control system installation
  • Gas collection and control system design plan
  • Gas control system equipment
  • Gas collection and control system performance
  • Methane destruction efficiency for flares and energy recovery control devices
  • Open flare systems
  • Landfill gas treatment and processing
  • Wellhead gauge pressure
  • Devices measuring gauge pressure
  • Instruments used to measure methane
  • Control device destruction efficiency
  • Gas generation flow rate calculation
  • Source testing for any gas control device or devices
  • Repairs and temporary shutdown of a gas collection and control system
• 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
  • Gas collection and control system shutdown and removal
• Reporting and recordkeeping requirements
  • Waste in place reporting
  • Landfill gas heat input capacity calculation and reporting
  • Surface emissions and component monitoring reporting
  • Reporting on gas collection and control system operations
  • 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
• Other requirements
  • Incorporating new statutory civil penalties for violation of the law and implementing rules
  • Adopting maximum methane concentration limits for both owners and operators of active and closed municipal solid waste landfills
  • Adopting exemptions for methane concentration limit exceedances due to activities defined in RCW 70A.540.050(3)
  • Establishing a method for landfills to claim exemption from the rule
  • Establishing a process for landfills to request approval of alternative compliance measures
  • Terms and definitions

This rulemaking applies to owners or 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, and inactive municipal solid waste landfills as defined in WAC 173‑408‑020. The adopted 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

If a municipal solid waste landfill partners with a third-party owner or operator, as defined in WAC 173‑408‑020, to operate all or a portion of the gas collection and control system or energy recovery device, the obligation to comply with the requirements of this chapter are the responsibility of the owner or operator of the relevant portion of the gas collection and control system or energy recovery device.

Landfill methane regulations adopted by the California Air Resources Board, the Oregon Environmental Quality Commission, and EPA informed Ecology’s rulemaking, as required by RCW 70A.540.020(3).