Abstract: A system for constructing underwater impermeable protective sheathings of hydraulic structures or parts of them. At least one reference line is provided on the surface area to be protected and a protective sheathing is constructed underwater by positioning and stretching impermeable sheet materials over the area, keeping one lateral edge of each sheet material parallely aligned to said reference line, and maintaining hydrostatic balanced conditions between the pressures on the front and rear faces of each sheet material; the sheets are afterwards watertight connected along their edges and anchored to the surface of the hydraulic structure by mechanical anchorage devices.

Abstract: A method and an assembly for protecting dams according to which dehydration of the dam body is obtained as a result of the differences in temperature between the concrete structure and a steam barrier defined by a water-proof protective sheathing. The condensation water and any seeping water is eliminated by means of a drainage channel system at atmospheric pressure.