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Biopile remediation is an ex situ version of soil bioventing, where contaminated soil is constructed into engineered piles or cells with the aim of enhancing conditions required for biodegradation through greater control of oxygen, nutrient such as phosphorus and nitrogen and water. The microbial activity of these microorganisms degrades hydrocarbon contaminants such as diesel that are adsorbed to the soil particles. Perforated pipes aerate the biopiles through blowing air into the soil or drawing air from the ambient atmosphere and in addition enable greater control of VOCs. Where considerable moisture may be present, a leachate collection can be installed, with the piles being constructed on impermeable geotextile membranes or clay layers in order to prevent the contamination of the surrounding land by such leachate. The piles, which may be covered with a man made cover to conserve heat and optimal conditions for the microorganisms, are also turned periodically in order to homogenise the soil and ensure complete aeration.