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A logical extension of the vadose zone sweeping described above <br /> would consist of a similar sweeping, together with the chemical <br /> treatment of the injected water to modify the geochemical <br /> conditions such as to render harmless and less mobile those <br /> metallic compounds which are presently incorporated within the <br /> ! <br /> $ soil moisture adherring to the particles in the vadose zone. <br /> Such treatment could be achieved by the imput of reductant <br /> s <br /> reagents into the proposed plug-flow displacement fluids to be <br /> percolated or injected. Such reductant reagents would convert <br /> the hexavalent chromium to the less toxic trivalVant state, and <br /> further immobilize the copper and arsenic which presently is <br /> ( immobile in the shallow regions of the vadose zone. <br /> Marley believes that in -situ treatment of soil contamination <br /> offers a promising, cost effective method of resolving these <br /> problems and is prepared to commit to a controlled laboratory <br /> evaluation to determine the potential of such remedial measures. <br /> Should such evaluations yield negative or inconclusive results, <br /> Marley is prepared to pursue other soil contamination remedial <br /> measures. However , if as anticipated , the laboratory <br /> investigatons yield favorable results , Marley would pursue this <br /> remedial procedure through field prototype demonstration to full <br /> scale application. <br /> 3. Removal of Contaminated Soils. Marley recognizes the <br /> '— possiblity that in -situ treatment methods could prove to be a <br /> less than fully acceptable solution at this site and is prepared <br /> I 26 <br />