Considering the magnitude of radioactivity concentrations in Ralston Creek and use of the stream as a primary water source for two water supply reservoirs - Ralston Reservoir and Upper Long Lake, Region VIII initiated a limiting monitoring effort to supplement the State/Water Board program. This monitoring activity extended over the period of May through September, 1972. Emphasis was placed on eliminating critical data voids; i.e., radioactivity concentrations in the waters of Ralston Reservoir and Upper Long Lake. In addition to the grab water samples collected from these impoundments, sample collection included the mine effluent, water and bottom sediment samples from Ralston Creek and Long Lake ditch, and bottom sediment samples from the two impoundments.