Hobart Landfill – Landfill Gas Control and Cover System Improvements
King County Green Bonds
The 35-acre landfill closed in 1994 with an engineered composite cover and an active flared gas collection system. A leachate containment and extraction system was installed and leachate pumping was discontinued in 1995. Groundwater and landfill gas monitoring are in place. A model airplane community group uses the property to fly model planes.
- Evaluate the existing shallow groundwater cutoff wall and extraction wells system to provide recommendations on modifications needed to protect the surrounding groundwater quality. Completed first phase of cutoff wall, landfill cover and groundwater. Initiating second phase to evaluate potential modification alternatives;
- Replace the existing landfill gas flare with a more efficient treatment flare to better handle the decreasing levels of landfill gas;
- Conclude improvements and provide property for additional secondary beneficial use.
- Gas and landfill cover/ slurry wall containment is 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 the collection and treatment of landfill gases;
- Achieving the above goals in order to minimize or terminate post-closure activities.
Green Bonds: 2017-Series A
$2.2m Green Bond Proceeds spent
10% reduction in GHG emissions MTCO2e/yr
Evaluation of Landfill Gas and Landfill Cover / Slurry Wall Containment is 70% complete.
Cover and cutoff wall evaluation will determine whether improvements are needed.
Groundwater quality shows continued improvements in water quality characteristics when compared with pre-Slurry Wall installation. Also, groundwater quality parameter are consistent when compared to their long term trends between 2019 and 2021.