Click the arrows to see a cross-section of an empty, partially full and full sanitary landfill. The base of a new landfill is above groundwater level and lined with a protective layer. A drain diverts leachate to a storage facility, with landfill gas vented or flared. Underground wells and above ground systems monitor the condition of groundwater and landfill gas levels. Once full, the top layer of a landfill is covered in grass.