Seepage Barrier

a structure designed to prevent water seepage, built into a foundation and in areas adjoining head-works; it is constructed by injecting various grouts into the soil through boreholes.

The main purpose of a seepage barrier is to reduce the rate of seepage and the loss of water from a reservoir and to reduce the pore pressure on the structure. Depending on the type of soil and its geological properties, seepage barriers are installed by cement grouting, hot and cold asphalt grouting, or by clay grouting (seeSOIL STABILIZATION). A barrier may be grouted in a vertical or inclined configuration under or near the headworks, or may be grouted in the shore of a reservoir. The barrier’s depth is determined by trial injecting water or air under pressure into a hole. The depth in some instances may be considerable, for example, 210 m for the Mauvoisin dam in Switzerland.