Abstract: A system and method of preventing groundwater contamination by a plume of liquid born toxic contaminants that includes establishing a dry barrier between a plume of liquid contaminants and the water table to immobilize the toxic contaminants. The dry barrier is formed by transporting dry gas into the barrier region, such as with injector wells, and then removing it and any moisture it has absorbed, such as with extraction wells to create a layer or bowl shaped structure that is so dry that liquid borne contaminants cannot pass therethrough. By maintaining the barrier, the contaminants form an immobile crust above the barrier which assists in prevention of liquid transport of contaminants into the groundwater. The system is particularly effective when radioactive contaminants are involved because the contaminants can remain fixed and undisturbed underground.