Trash disposal at landfills and dump sites consists of burying waste, either in an empty hole or within a purpose-built structure designed to isolate waste from surrounding soil and groundwater. Sanitary and municipal solid waste landfills utilize a clay or synthetic liner to isolate waste from neighboring environments. Landfills are typically designed to keep waste dry and protected from contact with the air.
Landfills consist of a bottom liner, trash disposal cells, a storm water drainage system, a leachate system that collects water that has percolated through the landfill, a system for collecting the methane created by decomposing waste, and a top cap or covering. Compacted trash is placed into storage cells, each of which typically contains a single day's waste. Prior to constructing a landfill, the soil composition, underlying bedrock and natural flow of water must be determined and studied in order to ensure the landfill will not pose a threat to the surrounding environment.
The environment within a landfill contains very little oxygen and moisture, which keeps the waste from breaking down rapidly. Landfills are designed to store waste over a very long period of time and environmental monitoring services are still performed for old landfills. Maintenance efforts for older landfills may continue for decades once they cease to accept new waste.