ABSTRACT: The waste material extracted after ore mining process is floated in the tailing dams within the mining plants. In order to prevent possible water seepage, the geotechnical characteristics of natural building materials of the dams and foundation soils must be determined for the design of reservoir. In this study, the reasons of water seepage from the waste disposal reservoir of Pb-Zn mining plant located at southern Çanakkale, Kalkım town were investigated. In this context, horizontal and vertical distribution and the permeability of the foundation soils at the reservoir areawere determined by trial pits, disturbed/undisturbed sampling and laboratory testing. The optimum water content and maximum dry density of the soils have been tested by standard compaction tests. Moreover, the permeability coefficient of the same soils was tested by falling head permeameter. The clay lining beneath the reservoir is properly compacted based on the related regulations with no permeability problem. However, the seepage from the reservoir is found to be due to the alluvial soils of the stream bed which is not excavated before the construction. Heavy metal and oxidated residual materials were observed in the stream bed. A total length of 100 m of the embankment located on the alluvial soil was removed. This portion of the embankment was re-compacted using the clayey soils with optimum water content and maximum dry density. The seepage from the embankment is completely prevented after re-compaction with a full reservoir