Earth and rockfill dams are usually designed with an impervious core consisting of fine graded soils. When suitable silts or clays are not economically available for the core, a concrete or bituminous facing is generally employed for the watertightness. As the facings deteriorate, water infiltration increases. With age and increased water infiltration, drains may become clogged because of transported fines. Uplift pressures will increase and dangerous internal erosion and potential piping of the dam may occur.

The installation of a synthetic geomembrane on the upstream face, with a drainage system behind,provides the following benefits:

- stops water infiltration

- provides watertightness even when large settlements occur

- can withstand seismic events

- reduces/prevents the formation of uplift pressures

- avoids the migration of fines in the core

- prevents internal erosion and piping In addition to being used as a remedial measure on both concrete and bitumen faced dams, the

CARPI geomembrane system has been specified on new rockfill dams, up to 90 m ( 270 ft) high as the only watertight element on the upstream face. In these cases ,the flexible synthetic geomembrane facing can be a valid alternative to a clay core providing the function of watertightness while aggregates of even less stringent properties provide structural stability. This solution may make projects feasible even when suitable aggregates are not available at competitive cost.

CARPI experience includes also the lining of the upstream face of cofferdams.