Abstract: An in-situ thermal desorption system which combines thermal desorption and vacuum extraction to separate organic compounds from in place contaminated soils is disclosed. A "heating blanket" desorption unit is applied directly to the surface of the hydrocarbon contaminated soil. The heating blanket assembly comprises of four basic components: a surface heating element, a thermal insulating mat, a vacuum collection system, and a vapor barrier. The surface heater, when energized, initiates a thermal front which moves down through the soil by thermal diffusion. As the soil is heated, organic compounds and water vapor are desorbed and removed from the soil matrix. A vapor collection system including a blower is fitted to the vapor barrier to establish a slight negative pressure inside the modular heating blanket units.