Roosevelt Regional Landfill
Superior engineering, vigorous regulatory compliance and environmental security are the core features offered by the Roosevelt Regional Landfill.
The natural geology below the arid hills of Klickitat County create an ideal location for the landfill including:
- 1,500 feet of separation from the bottom of the landfill to the closest regional aquifer.
- The geology separating the landfill and this regional aquifer includes 340 feet of low permeability natural clay.
- Tests of the clay demonstrate performance at 10-8 cm/sec, meaning it would take approximately 15,000 years for water to move through this barrier.
- A small, local aquifer 100 feet below the surface is confined to the site and provides responsive groundwater monitoring.
- The site receives approximately 6-9 inches of precipitation a year.
Additional Engineering creates a secure site:
- A secondary liner consisting of a two-foot thick, re-compacted natural clay layer (10-7cm/sec), or a performance based equivalent geosynthetic clay liner (GCL).
- A primary liner consisting of 80 mil high density flexible membrane liner (FML) which exceeds the regulatory prescribed 60 mil primary FML.
- A geotextile overlays the FML and is covered with highly permeable (greater than 10-2 cm/sec) aggregate for leachate collection.
- Comprehensive leachate and methane collection and control systems.
- An onsite power plant to convert the methane collected into electricity.
During the day the 200-foot working face of the landfill is the only exposed area. This area is covered nightly with daily cover. A combination of geo-membrane and topsoil will be used to close the landfill. Extensive monitoring systems will be kept operating for 30 years past the closure of the site. Upon closure the entire site can be returned to agricultural use.
H.W. Landfill Gas Power Plant
Leachate and methane gas are collected throughout the landfill by a system of pipes. The leachate is re-circulated through the landfill prompting rapid decomposition of waste and accelerating methane production. The methane gas is used to create electrical power.
Current methane production supports the generation of 10 megawatts of electrical power. The landfill may eventually generate 52 megawatts of electricity; enough power for roughly 30,000 homes!
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