Final cover is a multilayered system of various materials which are primarily used to reduce the amount of storm water that will enter a landfill

Landfill

A landfill site , is a site for the disposal of waste materials by burial and is the oldest form of waste treatment...

 after closing. Proper final cover systems will also minimize the surface water

Surface water

Surface water is water collecting on the ground or in a stream, river, lake, wetland, or ocean; it is related to water collecting as groundwater or atmospheric water....

 on the liner system, resist erosion

Erosion

Erosion is when materials are removed from the surface and changed into something else. It only works by hydraulic actions and transport of solids in the natural environment, and leads to the deposition of these materials elsewhere...

 due to wind or runoff, control the migrations of landfill gases, and improve aesthetics.

A final cover system can include a top soil layer composed of nutrient rich soil, a protective layer to reduce the effects of freeze/thaw, a drainage layer which moves storm water, a barrier layer, and a grading layer.

Cover integrity

For a final cover system consisting of a geomembrane, an analysis of the mechanical properties of the geomembrane should be conducted to ensure cover integrity is not jeopardized by localized subsidence, bending, and cover slope stability.

Localized subsidence

Localized subsidence induces tensile stresses in geomembranes

Geomembranes

Geomembranes are a kind of geosynthetic material made up of an impermeable membranes. Their use includes lining canals, ponds and also waste containment.-Composition:Geomembranes are made of various materials...

, which can threaten the final cover integrity. The magnitudes of the tensile stress can be viewed as a function of the dimensions of the subsidence zone and the properties of the cover soil. Allowable tensile stress of a geomembrane is usually known; in order to ensure the stability of final cover, the tensile stress allowable by a geomembrane should exceed the calculated value for tensile stress induced by waste.

Geomembrane bending

Geomembrane bending, both from its self-weight and soil cover may also induce tensile stress. Tensile stress from bending should not exceed the allowable tensile stress of the geomembrane.

Cover slope stability

Cover slope stability analysis involves evaluation of the interface strengths under static and seismic conditions. In order to perform an evaluation of the effects of a final cover system placed on a refuse side slope, infinite slope stability analyses are required. An infinite slope stability analysis assumes that the forces causing movement are due to the weight of the materials and the forces governing resistance are due to material strength. Most engineers design the permanent slope to have a minimum FS of 1.5, or 3H:1V, for static loading. Reductions in slope past a 3H:1V ratio, and thus decreasing the FS from 1.5, could possibly push GCLs beyond their limits of stability.