Alluvial sediments resembling tailings material derived from mining operations in the northern Black Hills of South Dakota were identified as covering in excess of 1100 hectares of land paralleling Whitewood Creek and the Belle Fourche River downstream of Lead, South Dakota, in 1971-72. The material assayed were 68 samples of shallow ground water collected from near the banks of Whitewood Creek and the Belle Fourche River. The results of chemical assay indicated that concentrations of mercury, zinc, copper, arsenic, and cyanide in these waters were not in excess of the limits placed upon waters used for domestic and agricultural purposes. However, the results of assay of samples from these wells and wells located along the Cheyenne River near Wasta, South Dakota, did indicate that selenium concentrations in excess of 0.020 mg/l were present in certain wells in the lower Cheyenne River Basin.