The plant under investigation produces light and heavy soda ash by means of Solvay method, and the production process is associated with the formation of highly saline waste, which can adversely affect all elements of the environment. In a view of existing threats, attempts are undertaken to limit the quantity and improve the quality of post-production sewage. The aim of the study is to determine the effectiveness of activities to protect water in the area of the "Soda Mątwy" Production Plant in Inowrocław. The assessment of their effectiveness was based on the analysis of current level of chloride concentration reduction at 4 measurement points around the plant and determination of the trend for further changes. In all piezometers, the concentration of chloride ions has decreased and showed the same tendency in subsequent years, which allows to conclude about high effectiveness of activities related to water protection.