How do landfills pollute groundwater?

Landfills are a great example of "Out of sight - out of mind" Once the final cover od soil and grass is in place the potential problems are ignored.

Wastes in a landfill can be broken down into several categories: * Inert * Toxic * Biodegradable * Soluble (leachable)

A properly designed waste disposal site is contained by liners and clay covers so that nothing gets in or out. A poorly designed system is more like a teabag.

So what comes and goes through a poorly designed site?

Water comes through from the surface. This speeds up decomposition and brings in oxygen to promote the growth of microorganisms.

The decomposing organics liberate methane gas (a powerful greenhouse gas). The gas flows out of the surface of the site to the atmosphere or travels with pores in the soil to local basements causing safety problems.

As the water seeps through the mass of waste it dissolves organics, salts and metals from the site. These flow down and into the groundwater where they degrade the potability and usefulness of the water in several ways. If the water flows out into a stream it can kill fish or eutrophy the water to promote algae growth