Environmentally acceptable waste disposal to fill a depression in the earth. Typically, non-hazardous waste is layered and compressed over a specific area of land. At the end of each working day the layer is covered with earth. Secure or sanitary landfills dispose of hazardous waste by burial. To prevent leakage or leaching of dangerous substances into the soil and water supply, holes or trenches are deeply dug and lined with impervious plastic sheeting.