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Characteristics of Clay Lining Soils

Waste management landfills are constructed to protect soil and groundwater from contamination from harmful leachate---damaging liquids in waste that seep into the ground. Many methods of leachate control and protection involve the use of clay liners, according to Kerry L. Hughes, Ann D. Christy and Joe E. Heimlich of the Ohio State University Extension. Most clay liners fall into three categories: single clay liners, double clay liners and composite clay liners.

  1. Single Clay Soil Lining

    • Single liners that utilize clay in waste management facilities are not designed to accept liquid tar, municipal garbage, paint or treated lumber. Single clay liners are less expensive to operate than other methods. Single clay liners use a base of compacted clay under a layer of sand or gravel and leachate collection pipe layer under a protective layer---soil or soft refuse such as rubber, paper and organic refuse---under solid waste.

    Composite Clay Soil Lining

    • Composite clay liners add a composite geotextile layer, which is woven material that traps particles but allows liquid movement, between the protective layer and the sand or gravel leachate collection layer. A geomembrane, which is a specialized sheet of plastic, goes between the leachate collection layer and the compacted clay layer to trap leachate at collection pipes. Composite clay liners are very effective at limiting leachate migration, according to Z. Moses Ravindranath and Dr. S. Shrihari of the National Institute of Technology in India.

    Double Clay Soil Lining

    • Double clay liners add a second sand or gravel leachate collection layer and a second compacted clay liner to composite clay liners. Some double clay liners also utilize a second geomembrane. Double clay liners are used in secure, or hazardous waste, landfills to ensure that all hazardous leachate is collected and stored in containers for later treatment. The second collection layer operates essentially as a leak detection system and backup emergency leachate collection layer.

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