The history of the Savage River dam site investigations is described as an example of the applicability of geology to engineering work even in places where the geology is very simple. The earth dam will rest on a series of well-consolidated beds of sandstone, sandy shale, and limestone of Paleozoic age. The beds are unfaulted and dip downstream at low angles. The water table is at or close to the surface throughout the reservoir area. Exposures are good; the zone of weathering is shallow.The factors that influenced the choice of site are presented in detail. The presence of a large alluvial cone along one bank of the stream narrowed the choice of available sites. Toward the close of the drilling campaign small caves were discovered in the limestone in which the spillway will be cut and which will form part of one abutment. The discovery caused the inclusion of an extensive grouting program in the design.Considerable quantities of shale will be removed from the spillway excavation. Largely as a result of geologic evidence, it was decided that this shale would prove sufficiently durable for use in the dam embankment. The decision led to important changes in design and will result in savings many times as great as the cost of the geologic investigations.