Which of these describes a bottom liner?

The correct answer describes a bottom liner as a crucial layer that prevents leaks from the landfill. Bottom liners are essential components of modern landfill design. They serve as a barrier situated at the base of a landfill to prevent leachate – the liquid that collects as waste decomposes – from penetrating into the surrounding soil and potentially contaminating groundwater sources.

The materials used for bottom liners, such as clay or synthetic membranes, are specifically engineered to have low permeability, effectively isolating waste and reducing environmental risks. This function is critical for compliance with environmental regulations and for protecting public health and the ecosystem.

In contrast, the other options do not accurately represent the role of a bottom liner. An exterior barrier for surface drainage would pertain more to erosion control and stormwater management rather than leak prevention. A filter for composting organic waste would imply a system designed to facilitate the breakdown of organic matter, which does not align with the purpose of a bottom liner. Lastly, a network of channels for groundwater implies a drainage system rather than a preventive measure against leaks, as the purpose of a bottom liner is to contain waste, not to facilitate groundwater flow.