Abstract: With the pooling of reservoir of the Kaleta Hydropower Station, the precipitated gel was found to be accumulated at the entrance of the spillway gallery near the base of the dam. The precipitated gel was sampled and laboratorial analyzed for its chemical component; microstructure and item composition. The mechanism of the precipitated material accumulation was investigated from its source and environment. It is concluded that the alkaline water seeped from the concrete dam was from the interaction of groundwater, concrete and soilcrete from the seepage slurry wall. The stability of the dam foundation can be improved by reducing the seepage at the spillway gallery.

Key words: Spillway Gallery, Water Quality Analysis, Precipitated Materials, Potential Effect, Dam Foundation Stability