The underground gasification of coal (UCG) can produce two environmentally significant sources of polluted water. The first of these is the gas condensate stream brought to the earth's surface during gasification. This source is characterized as having a high concentration of inorganic as well as organic constituents. Of most concern is the ammonia, phenol, coal tar, and total organic loads. Of less concern, but still significant are the sulfates, total dissolved solids, and some situation specific metallics. From an engineering perspective, this is an industrial waste water which represents handling and processing problems but is geographically contained. These waters can be thought of as possible point sources of pollution. The second environmentally significant source of polluted waters associated with UCG is the residual gas condensate left in the gasification caverns combined with inflowing, more dilute ground waters. These waters do not begin to equal the gas condensates in terms of constituent concentrations. Some of the constituents, however, do exceed environmental regulatory requirements or baseline conditions. These waters are more difficult to contain than are the condensates, and as such represent a potentially significant environmental problem. The working hypothesis concerning the formation and transport of these contaminants is that a small amount of gas condensate water remains in the cavern following gasification. In-flowing ground water with baseline chemical concentrations contacts, ash, char and heat altered coal surfaces. This causes a solubilization of organic and inorganic materials into the ground water which, because of locally altered flow patterns, flows into the UCG cavern. Ground water mixes with the remaining condensates to increase overall concentrations while adsorption, decay, ion exchange and further dilution by inf10wing ground waters generally lower these constituent concentrations. Once the water level in the cavern reaches the regional gradient, flow from the cavern is expected. This flow experiences further solubilization of pollutants as well as adsorption, dispersion generated dilution, ion exchange and biological decay as it flows into unaffected aquifer materials. If the concentrations of select constituents exceed the background levels, a pollutant plume is said to exist. The ultimate fate of the materials contained in the plume is an important environmental consideration. Laboratory studies have been conducted to determine the natural restorative properties of the materials in and around UCG sites (1.2). It is possible that these sites could be self-cleaning or require only token active restoration input from man. The first of these scenarios is called the "passive restoration" option and can occur only when kinetic time is less than hydraulic transport time. When this occurs the time needed to adsorb, disperse, exchange and/or decay the pollutants of concern is satisfied before the pollutant mass is transported away from the contaminated site. If the hydraulics of cavern fill and transport are sufficiently slow enough it is possible that no pollutants will ever leave the cavern areas since these caverns will not readily fill with water. What is needed is a series of tools to evaluate the filling properties of the caverns as well as the transport phenomena outside the immediately affected areas. The objectives of the research conducted during this period are to develop and/or apply first generation modeling approaches to the determination of the feasibility of passive restoration at the Hanna, Wyoming, UCG site. Activities included in this effort are: 1. Evaluation of analytic tools for problem definition; 2. Selection of simulation approaches for first year analysis; 3. Algorithm development; 4. Computer coding where necessary; 5. Model acquisition where appropriate; 6. Data review and parameter selection; 7. Model(s) selection and debugging; 8. Flow simulation; 9. Transport simulation; and 10. Annual report.