The project of the 1200 MW Rio Escondido Thermoelectric Plant, now under construction in northern Mexico, includes a 300-hectare (750-acre) cooling pond. The entire reservoir will be created by building a circumferential embankment and developing the total storage requirement above the natural ground level. The makeup water will be obtained at a high cost from the Rio Grande by means of a 30-km-long aqueduct with a maximum capacity of 2.5 m³/s. Severe restrictions were put on the allowable seepage.

This paper describes the geotechnical investigations performed for evaluation of the subsoil permeability and the final solution adopted: a clay liner compacted according to a nonstandard procedure. The results obtained in the laboratory and in a full-scale test pond (50 by 50 m) are also presented. During this study the limitations of some accepted tests were put in evidence, and some new techniques were developed.