At the construction sites, pollutants including suspended materials due to excavation and / or grouting are often transported into aquifers through considerable distance. Once groundwater is polluted, even if pollution were discontinued, an aquifer may remain so for years because of slow flushing action. Therefore the small velocity of groundwater may be taken notice in relation to pollution by hu man activities. Groundwater does not necessarily purify itself through any given distance or period of time. In the present paper, the influence of construction works on groundwater quality was examined with special reference to the circumstances of a presence of production well. Under the assumption that the aquifer is homogeneous, isotropic, infinite in areal extent, and is of the same thickness throughout, some numerical formulae were proposed to estimate both the necessary time for pollutants and the influence sphere of changes in groundwater quality. Because each aquifer has its own specific characteristic, it is also important that each case should be investigated individually.