Abstract: A biodegradation apparatus comprising an enclosed vessel for holding a large volume of soil contaminated with hydrocarbons. Air diffusers uniformly within the vessel force moistened air through the vessel thereby removing volatile hydrocarbons from the contaminated soil. Outgoing air is supplied to vapor phase bioreactor for the removal of hydrocarbon contaminants from outgoing air. The outgoing air is next supplied to a granular activated carbon filter system which absorbs remaining hydrocarbons and then expels non-polluted air into the atmosphere concluding phase one treatment of the hydrocarbon contaminated soil. Phase two treatment of the hydrocarbon contaminated soil is initiated by utilizing high pressure injection nozzles to force water with surfactant additives through the soil thereby forming at the upper portion of the enclosed vessel a supernatant which includes hydrocarbon contaminants.