The present paper provides the assessing scale of the actual state of the geoengineering complexes and the model for predicting the behavior of supporting structures. To predict accidents in geoengineering and water treatment facilities it is proposed to apply the results of the theory of catastrophe theory, fuzzy sets, chaos theory and the theory of possibilities for the selection of optimal models of system behavior for a particular situation. It is shown that determination the limit boundaries in which the operation of the system can exist is impossible without the consideration of geoengineering treatment facilities and their components as fractal structures, functioning under conditions of "chaos". To minimize risks of damages of sewage geoengineering systems the monitoring with measurement of the toxic gases concentration and comparing it with the obtained one should be provided. The use of models of internal and external corrosion which includes the elements of the theory of fuzzy sets helps to evaluate completely the state of water supply and treatment facilities network.