2020年大学英语四级考试报考指南：考试样题_第2页

　　Proposing the Landfill

　　For a landfill to be built, the operators have to make sure that they follow certain steps. In most parts of the world, there are regulations that govern where a landfill can be placed and how it can operate. The whole process begins with someone proposing the landfill.

　　In the United States, taking care of trash and building landfills are local government responsibilities. Before a city or other authority can build a landfill, an environment impact

　　study must be done on the proposed site to determine:

　　the area of land necessary for the landfill

　　the composition of the underlying soil and bedrock

　　the flow of surface water over the site

　　the impact of the proposed landfill on the local environment and wildlife

　　the historical value of the proposed site

　　Building the Landfill

　　Once the environmental impact study is complete, the permits are granted and the funds have been raised, then construction begins. First, access roads to the landfill site must be built if they do not already exist. There roads will be used by construction equipment, sanitation (环卫) services and the general public. After roads have been built, digging can begin. In the North Wake Country Landfill, the landfill began 10 feet below the road surface.

　　What Happens to Trash in a Landfill?

　　Trash put in a landfill will stay there for a very long time. Inside a landfill, there is little oxygen and little moisture. Under these conditions, trash does not break down very rapidly. In fact, when old landfills have been dug up or sampled, 40-year-old newspapers have been found with easily readable print. Landfills are not designed to break down trash, merely to bury it. When a landfill closes, the site, especially the groundwater, must be monitored and maintained for up to 30 years!