In-situ retorting of oil shale can cause degradation of groundwater resources when the spent shale is leached by re-invading ground water. Literature on this problem and on control technology for its mitigation is reviewed. Recommended research to evaluate this problem and develop control technology for its mitigation includes: 1) better definition of regulatory guidelines, 2) criticial evaluation of water availability for intentional leaching of large scale in-situ retorting projects, 3) characterization of leachate and examination of monitoring data from existing abandoned retorts at Tract C-a, and 4) development of modeling capability to predict long term effects.