In-situ decontamination of soil is accomplished by providing electromagnetic energy of relatively short wavelengths from an array of applicators (antennas), inserted into a borehole array that encompasses the contaminated zone. The borehole array geometry is designed according to the soil's thermophysical properties. Electromagnetic energy heating and heat transfer mechanisms are used to raise the temperature of the soil to the desired level for vaporization of contaminants while at the same time avoiding excessive heat loss from the much larger array size. Heating is maintained throughout the contaminated zone after the final temperature has been reached by proper compensation of the envelope heat loss. Contaminants are evaporated by the heating. Contaminant vapors are collected by vapor collection pipes and/or a gas cover over the soil being heated. The contaminant vapors are then reduced in volume to manageably safe levels and then treated and/or disposed of. The release of contaminant vapors from the soil may be enhanced by the application of sound energy to the soil.