CHAPTER 15 ENVIRONMENTAL CONCERNS: WASTES AND POLUTION. 495 vide little refuge for rodents and insects, and there is no reason why the area cannot be used for recreation. In fact, there is a ski slope in Michigan that was cre- ated by using this process(see Figure 15.7) Sanitary landfills are still not without problems. The production of leachates and contamination of groundwater can still occur if the clay seal breaks or if the landfill is located improperly. Some local governments have enacted legislation that requires sanitary landfills to be lined or double-lined with plastic liners Another concern is the possibility of explosions and fires caused by the accumula tion of dangerous amounts of methane gas created by the anaerobic decomposi tion of refuse. However, it should be noted that some communities have systems in place to harness the methane gas and use it as an energy source FIGURE 15.7 A state-of-the-art sanitary landfill Source: Miller, Jr, G. T(1989). Lfuing in tbe Environment Prindples, Connections and Solutions, 10th ed. Belmont, CA: Wadsworth Publishing Company When landfill is full layers of soil and clay seal in trash Electricity Methane storage generator and compressor building Topsoil building Sand treatment system Garbage Pipes colect explos Probes to detect methane gas used as methane leaks fuel to generate Compacted solid waste Garbage Synthetic line Groundwater Clay and plastic lining Clay to prevent leaks; pipes Subsoil collect leachate from bottom of landfill