The high price of land in metropolitan cities and also the urgent need for underground transportation systems encourage developers to go deeper in the ground to create structures which not only can carry the usual loads for such structures but which also resist the infiltration of water into them. Here geosynthetic solutions, using GCLs and different types of geomembranes, are dominant solutions where high hydraulic heads exist. We have waterproofed over 30 such structures, most of them under the ground water level.