This handbook comprises an update of volume 1 of the 1984 USEPA document entitled "Review of in-place treatment techniques for contaminated surface soils." The purpose of this handbook is the same as that of the original document - to provide state-of-the-art information on in situ treatment technologies for contaminated soils. Like the previous document, this handbook is written for the use of a varied audience with divers technical backgrounds.... An in situ treatment technology is defined as one that can be applied to treat the hazardous constituents of a waste or contaminated environmental medium where they are located and is capable of reducing the risk posed by these contaminants to an acceptable level or completely eliminating that risk. In situ treatment implies that the waste materials are treated without being physically removed from the ground.... The 1984 document consisted of two volumes. Only volume 1 is being updated by this handbook. The reader can refer to volume 2, however, for a still current and comprehensive discussion of the fundamental properties of soil/waste systems.