A pressure barrier liner is an assembly of low permeability membranes disposed on above the other. A region is encapsulated between each adjacent pair of membranes. A pressurized fluid such as air or water is introduced into a selected group of the encapsulated regions to pressurize them to a selected pressure or pressures, thereby ensuring that any flow through the membranes or through disruptions in the membranes will be from within the pressurized regions to the regions outside the membranes ...