In situ plasma magmavication is a powerful and expedient technique for melting soil that subsequently cools to form a glassy igneous rock. A nontransferred arc plasma torch provides temperatures exceeding 4000°C that can be positioned within boreholes as a means of ground improvement or for environmental restoration of contaminated soils. The process is similar to in situ vitrification by embedded graphite elec- trodes, yet the nontransferred arc is a considerably more efficient process. The artificial rock can be left in place or, alternatively, may be exhumed and stored. The effectiveness of plasma remediation on uncon- taminated and contaminated kaolin was investigated through a prelim- inary series of laboratory chamber tests with small dosages of chemical, biological, and nuclear surrogates. It is believed that the process pyrolizes organic contaminants, while locking the inorganic contami- nants within the glass matrix. Measurements in compressive strength, stiffness, porosity, and mass density verified the transformation of soil to rock with improved material characteristics. In the past two decades, global attention has shifted its focus on world resources as population increases have resulted in water, air, and land becoming valuable commodities. Issues that previously had been put aside in the race for technology, such as solid waste treatment, are now main concerns for most of the world’s govern- ments. The U.S. Environmental Protection Agency (EPA) has taken a step in this direction with the targeting of contaminated sites around the nation. Some of the common cleanup methods currently recognized by the EPA (1) include natural attenuation, incineration, air sparging, soil vapor extraction, bioremediation, soil washing, thermal desorption, electrokinetics, pump-and-treat, solidification/ stabilization, deep soil mixing, and in situ vitrification (ISV). How- ever, most of these methods are useful and applicable only to spe- cific contaminants and certain simple soil conditions. Figure 1 pre- sents a selection of technologies available for soil remediation. Difficulties occur if multiple contaminants occur at a site or if very complex geostratification, soil layering, or heterogeneity exists. Vitrification is the transformation of a substance, by heat, into a noncrystalline (amorphous) material. Of the remediation methods, ISV is the only individual technique that can address both inorganic and organic contaminants, regardless of soil conditions, as the in- organics become encapsulated within the molten slag and the organ- ics are destroyed by pyrolysis (1). Notably, ISV is expensive, slow, and limited to application depths of 6 m. An emerging alternative technology for intense thermal treatment is the nontransferred arc plasma torch. The concise cylindrical design of the nontransferred arc plasma torch lends itself to direct insertion in the ground to treat soil. Combining the capabilities of this plasma torch with in-place remediation of soil is a process called in situ plasma magmavication (ISPM). Both ISV and ISPM are one-step techniques that attempt to address both organic and inorganic contaminants, regardless of their concentrations or the type of soil matrix composition. The signifi- cant advantages offered by ISPM warranted further investigation into plasma magmavication of contaminated soils as a way to treat wastes that resist other treatment methods. The plasma torch design permits directional applications, as in the manner of a flamethrower, and thus allows for target-specific treat- ment. After magmavication, the molten region cools into an igneous rock, thus altering the engineering properties of the original geo- materials, including compressive strength, stiffness, porosity, per- meability, and unit weight. As such, the ISPM process may be used to create vitrified pile foundations, inclusions for slope stabilization, and underpinning piers, as indicated in Figure 2, or it may permit the construction of in situ barrier walls for containment of waste plumes and buried contaminants. In this paper, the concept of ISPM is intro- duced for melting in situ materials (natural soil or rock, contami- nated ground, or buried waste) from a bottom-to-top approach. It does not depend on soil composition, and it can be applied at any depth and location (target specific). To simulate ISPM in the labo- ratory, a plasma torch was used to vitrify columns in chambers of soil deposits seeded with known surrogate contaminants. Forensic tests were used to evaluate the residuals after the process. PLASMA TORCHES Plasma exists as a highly ionized gas having temperatures between 2000°C and 20,000°C. It occurs in nature in the form of lightning. Under controlled systems, plasma is produced by a special torch that applies direct current to two copper electrodes. The resistance of the electrical arc within a gaseous medium creates a highly energized plasma state. Various types of gases can be used, but compressed air was used here because of its availability and economic advantages. A water cooling jacket protects the torch from self-destruction. In plasma technology, there are two primary types of torches: transferred and nontransferred. The transferred arc torch has both interior and exterior electrodes, with the arc flowing out of the device into a molten pool. This type of torch is generally used in closed furnaces and melter systems, such as steel manufacturing and metal recycling applications. The nontransferred arc torch has both electrodes inside the torch, whereby the rear electrode is connected as positive (anode) and the front electrode is negative (cathode). The “flame” that emanates from the torch is actually the curve of a j-shaped plasma column. This particular torch design is a reverse- polarity concept developed for NASA to simulate high temperatures during reentry of the space shuttle into the atmosphere (2). The dis- tinctions of this design are that it allows for smaller torch diameters Remediation and Transformation of Kaolin by Plasma Magmavication Josepha D. Celes and Paul W. Mayne J. D. Celes, Hart Crowser Inc., 1910 Fairview Avenue East, Seattle, WA 98102- 3699. P. W. Mayne, School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0355. Transportation Research Record 1714 ■ 65 Paper No. 00-0915