Today, hydraulic structures are constructed with high costs to optimize the use of water resources. Lack of adequate technical, social and economical studies are led to expend unusual costs during maintenance and operation of hydraulic structures. Most of the hydraulic structures are constructed in areas with poor water quality (i. e. acidic, basic and saline water). Engineering properties of fine-grained soils, especially the clay soils, depend on several factors such as density, porosity, structure, stress history, moisture content, texture, the quality of pore water solution and amount and type of clay minerals. So that any change in the one of these properties is led to change in physical and mechanical properties of soil and cause to damage of structures. Despite of extensive researches in different soil characteristics, there is not comprehensive study especially about the effect of pore water chemical quality on soils engineering behavior. In this study, the effect of acidic, basic and saline water on soil engineering properties were investigated. NaCl with 5 different levels (0.1, 0.21, 0.41, 0.72 mol/L) and the acidic and basic solutions with 7 different levels of pH (4, 5, 6, 6.5, 9, 10, 11) were added to the soil samples and mechanical properties of soil (including compaction characteristics, shear parameters, unconfined compressive strength, atterberg limits and compaction) were investigated. The results showed that the addition of NaCl did not change the volume unit weight and optimum moisture content of the soil. However, the angle of internal friction and unconfined compressive strength increased up to 10% and 23%, respectively. Also, increase of water salinity reduced the soil cohesion and liquid limit (LL) of soil but had no effect on the plastic limit (PL). Changes in soil pore water pH increased, 9, 28 and 61percent of angle of internal friction, cohesion and unconfined compressive strength of soil, respectively. But had no effect on unit weight and optimum moisture content of the soil. The acidic and basic water solution increased the liquid limit of soil, however did not effect on plastic limit. Keywords : Water Pollution, Clay, Salinity, pH, Soil Strength, Consolidation, Compaction, Atterberg limit