They range from burning to burying it in sanitary landfills. The current design of landfills does not promote the breakdown of wastes but does help to reduce their environmental impacts. In New York State, all new landfills have a plastic and clay liner at least 10-feet thick under the garbage, and a 4-foot thick cover over the top. These layers minimize the immediate environmental impacts of landfills but exclude the water, air, and temperature changes needed to degrade waste. Still, some degradation takes place over time, and leachate must be collected. (Leachate is the contaminated water that seeps out of landfills.) Each modern landfill in New York State has a leachate collection system to help keep the leachate from polluting groundwater and surface water supplies.