The water pollution potential of processed oil shale residues is a major concern regarding the environmental impact of oil shale development. Salts, trace elements and organics including carcinogenic polycyclic weathering. These materials, when entering the surface water and groundwater, may pose a serious problem to public health and the environment. Despite the relatively low concentration of the benzene soluble organics in spent shale, 200-2000 ppm, the large quantities of retorted shale that will be produced during a full day of production will contain 17-170 metric tons of benzene soluble materials per day. Schmidt collerus found that 20-40 degrees C of the total benzene soluble organic matter in shale can be leached by water and that most of the carcinogens in the shale were dissolved and concentrated in the salt residue.