Ironically most proper landfills (at least in the first world) use plastic liners along with clay as part of their barriers to prevent water contamination from

Ironically most proper landfills (at least in the first world) use plastic liners along with clay as part of their barriers to prevent water contamination from other trash. I am no expert - so I cannot say if the barriers put plastic in the groundwater but that method prevents more acute toxins like dioxins and oil from getting in.