Vashon Island Landfill – Landfill Gas Control and Leachate Collection System Improvements
King County Green Bonds
The 24-acre landfill closed in 1999 with an engineered composite liner, leachate collection (gravity pipes with an aeration pond), and gas collection with activated carbon filters. Storm water drainage and groundwater, surface water, and landfill gas monitoring are in place.
- Identify improvements needed to the leachate collection, cover and landfill gas system to address impacts to groundwater. This project will be completed in 2025 with recommendations for needed improvements;
- Conclude improvements and provide property for secondary beneficial use.
- Approximately 50% 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 the collection and treatment of landfill gases;
- Achieving the above goals in order to minimize or terminate post-closure activities;
- Installed 3 LFG extraction wells to LFG capture and minimize LFG to groundwater interaction;
- Remedial Investigation was completed in 2020.
- Installed new groundwater monitoring well to define extent of contamination.
Green Bonds: 2017-Series A
$2.2m Green Bond Proceeds spent
MTCO2e/yr: in progress
5% improvement in key water quality parameter per year