In addition to the more usual organic and inorganic liquid waste disposal problems encountered at many industrial installations, the uranium milling industry produces large quantities of solid wastes in the form of radioactivity laden sand tailings pile material. This report evaluates the radioactivity content of uranium mill tailings piles in the Colorado River Basin, evaluates their radioactivity water pollution potential insofar as this is possible, and on a case-by-case basis, indicates feasible and desirable remedial measures for controlling and limiting the spread of radioactivity from the piles.