The regulations governing the construction of landfill cells prescribe maximum levels of permeability for the liners.  Typically a landfill cell will consist of two liners, one of which would be HDPE, and the other an impermeable clay ( where locally available ) or a BES ( Bentonite Enhanced Soil ) mix ( where a suitable clay is not locally available ).  The Bentonite imparts low permeability to sand or other permeable soils ( referred to as the "host" material ) when correctly mixed with the host and applied.

Kentish Minerals' grades

KM2

KM2E

KM-A

Have all been supplied extensivelyfor this application in both the UK and Ireland.