Hitting the Curve - Riphshin Lake Dam Repairs

Ripshin Dam is a 42 feet (12.8 m) tall earthen dam located in Roan Mountain, Tennessee that impounds a 56-acre (22.7 hectare) private residential lake. The dam was constructed in two stages from 1927-1928 and 1945-1946. Dam repairs were made in 1995 that included raising the dam about 4.5 feet (1.7 m), installation of drainage improvements, and constructing a concrete chute spillway. In 2021, S&ME began consulting for a siphon replacement for the dam. Additional challenges (i.e. curve balls) were discovered during the dam stability evaluation, design, and construction. This included replacement of the dam siphon, presence of semi-hydraulic fill in the dam, other poor embankment fill, unplanned partial removal of a historic conduit within the dam, limited site construction access, temporary dewatering issues, mountain weather, extended lake dewatering costs, and finally passing Hurricane Helene flows without the use of the primary spillway. These challenges significantly affected the dam repairs construction schedule and costs. The challenges encountered also remind us that differing site conditions and geohazards may be encountered that must be addressed during construction using the Observational Method described by Karl Terzaghi.