An engineering assessment was performed of the problems resulting from the existence of radioactive uranium mill tailings at the Green River site, Utah. The services include the preparation of topographic maps, the performance of core drillings and radiometric measurements sufficient to determine areas and volumes of tailings and other radium-contaminated materials, the evaluation of resulting radiation exposures of individuals and nearby populations, the investigation of site hydrology and meteorology and the evaluation and costing of alternative corrective actions. Radon gas release from the 123 thousand tons of tailings at the Green River site constitutes the most significant environmental impact, although windblown tailings and external gamma radiation are also factors. The three alternative actions presented are dike stabilization, fencing, on- and off-site decontamination and maintenance; improvements in the stabilization cover and diking plus cleanup of the site and Browns Wash, and realignment of Browns Wash; and addition of stabilization cover to a total of 2 ft, realignment of Browns Wash and placement of additional riprap, on-site cleanup and drainage improvements. All options include remedial action at off-site structures. Cost estimates for the three options range from $700,000 to $926,000.