Granular drain system

The production of contaminated leachate is a possibility with most disposal sites. Leachate consists of water that has become contaminated by wastes as it passes through a waste disposal site. It contains waste constituents that are soluble, not retained by soil, and not readily degraded chemically or biochemically. Therefore, new hazardous waste landfills require leachate collection/treatment systems, and many older sites are required to have such systems retrofitted to them. Leachate is collected in perforated pipes that are embedded in granular drain material. 

Modem hazardous-waste landfills typically have dual leachate collection systems, one located between the two impermeable liners required for the bottom and sides of the landfill, and another just above the top liner of the double-liner system. The upper leachate collection system is called the primary leachate collection system, and the bottom is called the secondary leachate collection system. Leachate is collected in perforated pipes that are embedded in granular drain material. 

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