An extensive dewatering program has been implemented at the toe of Saluda Dam near Columbia, South Carolina. Dewatering is required to lower pore pressure within the existing dam during construction of a new back-up dam, as well as, to lower water levels below the excavation bottom. Over 80 deep wells, numerous shallow wells, and hundreds of jet-eductors were installed to remove groundwater. Hundreds of open standpipe piezometers and vibrating wire piezometers were installed to monitor phreatic levels and pore-pressure. Successful dewatering required a clear understanding of the subsurface geology and surface topography before the original dam was built.