The purpose of the article is to present a methodological approach to assessing the state of the risk to the environment from man-made emergencies at chemically hazardous sites. The methodological approach is based on an expert method, the use of which allowed the authors to create the structure of the risk management system and, determine the plurality of criteria parameters while taking into account their weight in the formation of the environmental consequences of chemical accidents. Criteria parameters were grouped into clusters of physicochemical and toxicological properties of hazardous chemicals used at a chemical plant, equipment operating at an enterprise, personnel, and environmental vulnerability. The research became the basis of the Guidelines for Assessing the Environmental Risk from Emergencies at Chemically Hazardous Sites. As an example, the article presents the calculation of the level of environmental risk for a terrestrial site from the metallurgical enterprise LLP Kazakhmys Smelting, in Zhezkazgan town, Republic of Kazakhstan. The developed methodology is the basis of the Information and Analytical System for Assessing the Environmental Consequences of Man-made Emergencies, which allows users to facilitate the implementation of a set of measures aimed to forecast and reduce the impact of emergency’s damaging factors on the environment.