GroundwaterWater held in the ground below the site. The liner is there to protect it.
Clay linerCompacted clay on the bottom and sides of the pit.
GeomembraneA flexible plastic sheet laid over the clay. The two together make the composite liner.
Leachate pipeIt collects leachate for treatment. Leachate is rainwater that has filtered through the waste.
Compacted wasteWaste is spread and compacted in layers.
Daily coverA layer of soil spread over each day's waste.
Final cover (cap)The cover placed over a full landfill. It keeps rain out.
Gas wellIt draws landfill gas out of the waste.
FlareCollected gas that is not used for energy is burned here.
How this list was compiled: Every name checked on 2026-10-01 and kept only where two of these use it. (1) US Environmental Protection Agency, Municipal Solid Waste Landfills, https://www.epa.gov/landfills/municipal-solid-waste-landfills , and Basic Information about Landfills, https://www.epa.gov/landfills/basic-information-about-landfills : composite liners, a flexible membrane (geomembrane) over two feet of compacted clay soil lining the bottom and sides, to protect groundwater and the soil from leachate; leachate, formed when rainwater filters through wastes; leachate collection and removal systems on top of the liner; compacting and covering waste frequently with several inches of soil; daily cover; final cover and closure; groundwater monitoring wells. (2) US Environmental Protection Agency, Landfill Methane Outreach Program, Basic Information about Landfill Gas, https://www.epa.gov/lmop/basic-information-about-landfill-gas : landfill gas, roughly half methane and half carbon dioxide, is extracted using a series of wells and can be flared or used for energy. (3) Wikipedia, Landfill, Landfill liner, Daily cover, Leachate and Landfill gas, text only, https://en.wikipedia.org/wiki/Landfill and https://en.wikipedia.org/wiki/Landfill_liner : compacted clay overlaid by a geomembrane; waste compacted on the working face and covered daily; daily cover, a layer of compressed soil over a day's waste; the cap placed on a full landfill to keep out precipitation; gas wells and flaring. Licence: own work
The drawing: Own drawing from plain geometry; nothing traced. Not to scale. Licence: own work
How it works
A sanitary landfill is an engineered site, not a hole in the ground. The drawing cuts one open from the groundwater up to the grass on top and names nine parts.
Read the full guide
Keeping liquid in
Rain that filters through waste becomes leachate. To keep it out of the groundwater, the bottom and sides are lined with compacted clay and, over the clay, a plastic sheet called a geomembrane. Pipes on the liner collect it for treatment.
Filling and closing
Waste is compacted and covered with soil, the daily cover. When the landfill is full, a final cover, or cap, goes over the top. Buried waste gives off landfill gas, so wells draw it out to be burned at a flare or used for energy.
As a landfill cell diagram this is not to scale: the liner is far thinner than shown.
The quiz accepts plastic liner or flexible membrane for geomembrane, and landfill cap for final cover.
Questions and answers
What are the parts of a landfill?
From the bottom up: a liner of compacted clay and plastic sheet, a leachate collection system, layers of compacted waste under daily cover, and a final cover on top. Gas wells run down into the waste, and wells nearby are used to test the groundwater.
What is leachate?
The liquid formed when rainwater filters through the waste in a landfill. A collection system on top of the liner removes it for treatment.
What is the liner of a landfill made of?
Modern landfills use a composite liner: a flexible plastic membrane, the geomembrane, laid over a layer of compacted clay. It lines the bottom and sides to protect groundwater and soil.
What happens to the gas from a landfill?
Landfill gas is roughly half methane and half carbon dioxide. It is drawn out through wells and then either burned at a flare or used as fuel in an energy project.