The object of this study was to evaluate control technologies for groundwater pollution resulting from leaching of modified in-situ spent shale. Preliminary engineering analysis was used to identify control technologies which were technically feasible and cost-effective. Process modification, intentional leaching, and retort grouting were further evaluated using numerical modeling and experimental techniques. Numerical simulation of the geohydrology at tracts C-a and C-b was used to determine the flow regime during and after processing, the amount of water available from dewatering, and the time scale of groundwater reinvasion. It was found that reinvasion would take over 200 years and that dewatering flows would probably be insufficient to satisfy water requirements for retort grouting. The formulation of low-cost grouts based on surface-retorted spent shale was studied experimentally. A high-strength hydraulic cement was produced by calcining Lurgi spent shale with an equal amount of CaCO/sub 3/ at 1000 C for 1 h. Electrical conductivity measurements indicated that the leachate from a grouted retort would be more concentrated than that from an ungrouted retort, but the increase in concentration would be more than offset by the reduction in flow. A standard flow-cone test used for grouting of preplaced aggregate concrete was used as the criterion for grout fluidity. This criterion was achieved by inclusion of either 33 percent sand or 0.25 percent lignosulfonate fluidizer in the grout. These grouts were found to be Casson fluids with yield stress values about 60 dyne/cm/sup 2/. Intentional leaching of MIS retorts was evaluated by developing a mass-transfer model of the leaching process. The model was experimentally verified for total organic carbon and used to calculate that 2.1 to 3.4 pore volumes would be needed to reduce leachate concentrations to 10 percent of their initial value.