This paper makes an attempt to find the impact of the construction of underground metro rail corridor on the water quality parameter pH below the ground surface. This massive construction which is constructed very deep from the ground surface tries to alter the properties of groundwater regime and the chances of polluting the water are very high. The water quality parameters which are naturally available below ground surface also get altered. This paper discusses about the impact on water quality parameter pH due to the construction of underground metro rail corridor and its pollution level in the groundwater. The water quality data collected are divided into before, during and after the construction of corridors. Spatial analysis using GIS is carried out to predict the changes in three phases. The pollution of pH seems to be more than 7.5 after tunnel construction when compared to undisturbed soil surface.