The short characteristic of engineering-geological and hydrological conditions of the grounds of concrete constructions is given. Factors of formation of ecological conditions in a benthonic zone of a water basin of Cheboksary hydroelectric power plant are analyzed. Dynamics of change of activity and number of microorganisms in water and bed deposits of a water basin is considered. Results of specialized shooting in dry footway about a condition of concrete of a hydroelectric power plant building of and an overflow dam in 2010-2011 are stated, the comparative estimation of microbiological activity which promotes development of the vigorous activity of biocorrosion of concrete and metals is spent. It is shown high microbes prevalence the materials applied to repair work (seals of various defects in concrete designs).