During the excavation of the tunnel one of the greatest problems that can be encountered is related to the presence of groundwater. One issue that can arise from that, is the possibility of having uncontrolled volumes of water incoming into the underground excavation. Dealing with rock masses, critical inflows can be encountered when the excavation crosses discontinuities, weathered zones or faults. The degree of the inflow will depend on the aperture and other properties of these discontinuity zones being the intact rock an impervious medium. Water inflow in addition to creating unpleasant conditions underground for the workers, it also cancause problems of settlements on the surface.