CONTRIBUTIONS TO HYDROGEOLOGICAL PROTECTION PERIMETER SIZE CALCULATION UNDER SEVERE AND RESTRAINING REGIME

Starting from the observation that the self-purification processes in aquifers is negligible and the most intense water pollution phenomena occur, in fact, in the layers above the aquifer, the paper presents a method for calculating the required time for a pollutant particle potential traverse the layers above the aquifer. The method is based upon constitutive equations of unsaturated porous medium, the harmonic composition law for equivalent hydraulic conductivity and on Gardner's equation to calculate the variation of vertical load standpipes, psi . It involves determining the hydrodynamic load and the velocity gradient apparent and real - which leads to the calculation of the time to go to each of the aquifer coating. Once this time known, we believe that it should be summed with the travel time of contaminated water in aquifer, calculated by the methods already established before. Therefore, the distances of the sanitary protection area will correspond to the rated "transit time" (20 days under severe conditions and 50 days under restriction regime) decreased with the time, Tt, which is the time needed for the particle to get through the distance between the ground surface and the groundwater level.