The earth dam of the Istra hydroelectric complex is dry-drained of sandy soils. Its water level is 20 m below the crest. Soils in the body of the dam are in overconsolidated state. Sounding was conducted only to the depth of 1,5-2,0 m. Overconsolidated sands correspond to weakly cemented sandstones, in which it is impossible to introduce static and dynamic probes.