49·UN盯 FOUR ENVIRONMENTAL HEALTH AND SAFETY FIGURE 15.6 Household waste picked up at the curbside with a segregated container, recycling truck location, and depth of groundwater and little concern for neighbors. These open dumps, while cheap and convenient, were unsanitary because they supported open pits in whic large populations of rodents, flies, and vermin. Such dumps also produced leachates, liquids created when water mixes with wastes and removes soluble constituents from them by percolation, which too often found their way into underlying groundwater Dumps were a health hazard and reduced the value of adjacent property because of their obnoxious odors, their unsightliness, and their generally unsanitary conditions. ater mixes w The passage of the Resource Conservation and Recovery Act of 1976 soluble constituents(RCRA, pronounced Rick-Rah) provided legislation that phased out open dumps from them by and required that the disposal of solid waste be done in sanitary landfills. Unlike dumps, sanitary landfills are supposed to be located at sites that can geographically and geologically support them, sites with natural clay soils. If clay soil cannot be found, a clay lining must be constructed to prevent leachates from reaching groundwater. Sanitary landfills are not to be located over sand or gravel deposits ation nd Recovery Act of that would allow leachates to reach ground water. Second, in sanitary landfills all refuse is spread and compacted in thin layers by bulldozers. Once the compacted the federal low that sets forth guidelines layers are about eight to ten feet thick, they are covered with about six inches of soil, compacted again, and readied for another ayer of refuse. At the end of each andling nd disposa day, unlike an open dump, refuse is covered with a layer of soil. This process con of hazardous wos tinues until the landfill is full, at which time a final layer of soil about two feet thick is placed on the top. When this process is strictly followed, sanitary landfills pro-