Ukraine is in a crisis regarding the development of critical infrastructure objects. The main factors contributing to this situation include military actions, systemic underfunding, insufficient maintenance, and infrastructure deterioration. This not only complicates the fulfillment of key socio-economic functions but also poses threats to national security. As a result, there is a need to develop a methodology for assessing the risks of emergencies at critical infrastructure objects. The goal of this study is to develop a methodology for assessing the risks of emergencies at critical infrastructure (CI) objects and to implement it using the example of the "Donets" water treatment complex. The research results include a developed algorithm for quantitative risk assessment of CI and its elements, enabling the evaluation of all threats and the analysis of potential threat realization scenarios. It has been established that, in many cases, the failure of a single system element significantly affects the ability of other elements and the object as a whole to perform their functions. A new approach has been developed and implemented for identifying and assessing risks in the critical infrastructure sector related to life-support systems, specifically water supply. This approach allows for the identification of potential vulnerabilities of the object to various threats while considering possible cascading effects. The study provides probabilistic estimates of event developments based on predefined scenarios for the «Donets» water treatment complex.