There are several reasons why soil, sand, or rock is used to cover garbage at a sanitary landfill.
- To compact the garbage - this increases biodegradation for some components and prevents the landfill from rapidly filling with uncompressed refuse
- To isolate the garbage - this limits the availability to scavengers such as birds and rats, which may carry contaminants from the landfill
- To reduce the evaporation and aerosol release from the site - it will usually decrease the odors from the site and reduce the affected area
- To absorb liquids from the trash to limit their release into groundwater or as runoff (many landfills have impermeable liners to reduce soil leaching)
