What Is a Permeable Layer, and Why Do Landfills Need Them?

What Is a Permeable Layer?

A permeable layer is a blanket or membrane designed to line the bottom of a landfill. It helps keep landfill waste from contaminating local water sources by collecting and absorbing most of the liquid that passes through it.

How Does A Landfill’s Permeable Layer Work?

The permeable layer functions similarly to a coffee filter or cheesecloth, allowing air and gas through but trapping most liquids. These membranes are usually made from geosynthetic clay materials, which have tiny little holes in their composition that let some things through while keeping others out. If you try hard enough, you could probably pass a toothpick through them, but not much else slips through without causing too much damage.

It is important that permeable layers be extremely permeable, as not to fail under the pressure of landfill waste. If permeability is too high, it would allow liquids to flow through too quickly and leave nothing for runoff treatment plants to clean up. A permeable layer that’s permeability is too low could create a watertight barrier between the permeable layer and landfill waste. This creates a risk of leaks in case landfill waste were to shift or settle.

There are three ways permeables layers deal with this balancing act:

  • Using permeable material with permeability that is tailored for the specific landfill.
  • Using permeable material with different permeability on each side of the membrane.
  • Using more than one permeable layer to achieve the desired permeability, which is designed to fail under pressure of landfill waste. This helps prevent leaks.

Permeable layers are only used at landfills that process solid, nonhazardous waste. Hazardous landfill waste can contaminate soil and water if it were to slip through permeables layers, so special care must be taken in their design. Closing these specialized landfills usually include removing the permeables layers so as not to leave an environmental hazard behind.

Why Do Landfills Need Them?

Landfills can be dangerous places where you’re highly likely to get sick just by being near them. Part of their danger comes from the risk of groundwater contamination via corroding liquids that filter through permeables into wells, streams, rivers, and ponds nearby. Most of their danger comes from toxic fumes from landfill decomposed waste. Liquid permeable layers help keep groundwater safe from landfill leakage.

In addition, permeable layers help keep landfill gas from permeating into the sky where it can form smog and contribute to ozone depletion. These gases are often composed of methane, which is a greenhouse gas with a global warming rate twenty five times higher than carbon dioxide.

At Midwest Companies, their engineered construction aggregate substitute permeable layer is designed with permeability tailored to the specifics of your landfill. They also offer permeables with different permeabilities on each side of the membrane for maximum permeability at minimum weight. Contact them so they can help you design a solution that keeps your landfill safe and environmentally friendly.