Abstract: The present invention relates to the method of `in situ` collection and treatment of floating, sinking and dissolved contaminants in a soil environment which involves forming an in-ground diversionary water barrier as a boom around at least a portion of the waste site on the down-gradient side of the in-ground water flow, as a bottomless tank that through water removal creates an in-flow or in-gradient condition causing water to flow into and up in the tank area, or to control the downward flow and eventual discharge but control the detection time within the bottomless tank. The barrier involves forming an in-ground diversionary temporary water barrier as a boom around at least a portion of the waste site on the downstream side of in-ground water flow. The barrier preferably extends at least as deep as the in-ground contaminated water flow into the aquifer.