A typical cap stacks a gas venting layer, a barrier such as LLDPE geomembrane or a GCL, a drainage layer and cover soil that supports vegetation. It must tolerate settlement as the waste decomposes, so flexible geomembranes and textured surfaces for slope stability are common. Caps usually fail by sliding on a weak interface, losing cover soil to erosion or drowning a drainage layer in storm water.
Cap goes in this summer, 40-mil textured LLDPE with a drainage composite and two feet of cover.
Also heard as
- final cover
- cover system
- closure cap
Related terms
LLDPE
Linear low-density polyethylene: a softer, more flexible geomembrane polymer that follows uneven ground better than HDPE.
Geocomposite
Product that combines two or more geosynthetics, most often a geonet core with geotextile bonded on one or both sides.
Interface friction
Shear resistance between a geosynthetic and soil, or between two geosynthetics, that keeps lined slopes from sliding.
Bathtubbing
Water or leachate collecting inside a lined area because more gets in from above than can drain out below.