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Green bonds: Enumclaw Landfill

Enumclaw Landfill – Achieve Termination of Post Closure Status

King County Green Bonds

Enumclaw Landfill
Enumclaw Closed Landfill

The 39-acre landfill closed in 1993 with a composite geomembrane cover and soil cover planted with grass and trees. A landfill gas collection system with a flare was installed at closure and was updated in 2017. The flare and blower has been turned off currently to support transitioning from active to passive LFG collection system. Stormwater control, groundwater, and landfill gas monitoring are in place.

Project goals

  • Collaborated with regulatory agencies to improve the effectiveness of the groundwater monitoring program to obtained authorization to minimize groundwater sampling;
  • Received regulatory approval that landfill has little to no settlement, a requirement for termination of post-closure;
  • Achieved landfill gas concentrations below regulatory standards though active landfill gas collection and treatment and were granted regulatory permission to end landfill gas treatment;
  • Biofiltration system has been initialized for the further reduction of greenhouse gasses. This pilot project will be completed by mid-2022;
  • Conclude improvements and provide property for secondary beneficial use.

Percentage completion

Concluding improvements and achieving of post-closure criteria is approximately 80% complete;

  • Settlement: 
    • received regulatory approval for cover settlement stability, 100% complete.
  • Landfill Gas:
    • received PSCAA approval to end treatment;
    • running test project in order to move to passive collection, 85% complete.
  • Ground-water/Leachate:
    • received regulatory approval to decrease sampling frequency and to sample for fewer analytes, approximately 70% complete.

Key environmental attributes

  • Groundwater quality improvements to meet regulatory compliance that are protective of human health and the environment, through improvements to the environmental control systems;
  • Reduce the potency of GHG emissions to the greatest extent feasible, through biofiltration of landfill gases;
  • Achieving the above goals in order to minimize or terminate post-closure activities.

Project info

Green Bonds: 2017-Series A

$1.1m Green Bond Proceeds spent

20% reduction in GHG emissions tCO2eq/yr

Annual Energy Savings KWh Trend analyses show that groundwater quality improved by 1% between 2020 and 2021 with most monitoring wells demonstrating stable conditions.

CICERO independently rates King County Green Bonds.
Download Cicero's analysis
Cicero Deep Green

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