How long should the infiltration layer of a final cover system typically be?

The infiltration layer of a final cover system is designed to minimize water infiltration into landfill waste, thereby reducing leachate generation and potential groundwater contamination. A thickness of at least 18 inches of earthen material is recommended because it provides sufficient mass to limit the movement of water and promote drainage.

This thickness also allows for the establishment of vegetation and supports the growth of root systems, which can help in stabilizing the cover and further reducing erosion. An adequate infiltration layer acts as a barrier, protecting the underlying waste from moisture while promoting the natural processes of evapotranspiration.

While other thicknesses might seem reasonable, 18 inches strikes a balance between effectiveness and practicality, making it the standard practice in landfill cover design.