Retaining walls made of reinforced concrete are widely used in hydraulic engineering and transport construction. Since their rear faces are covered with ground filling, it seems difficult to control the stressed state of the rear working fittings, which in some cases led to deviations in the work of structures from the project. In this article, corner type retaining walls are considered. The purpose of the work was to develop and test an engineering technique for determining the stress state in horizontal sections of retaining walls made of reinforced concrete. In the framework of this work, studies were conducted on the structures of reinforced concrete retaining walls that interact with the soils of the base and backfill. At the same time, using the provisions of structural mechanics and the theory of reinforced concrete, an engineering technique was developed that allows calculating the stress state of reinforced concrete retaining walls along horizontal sections. To test the proposed calculation methodology, the in-situ data of instrumental surveys of the operated lower retaining walls of the PSPP water intake (pumped storage power plant) were used on the basis of the «reinforcement unloading» method in relation to the facing structural reinforcement of the walls. The developed method was practically implemented to assess the effective tensile stresses in the rear working reinforcement, as well as the compressive stresses in the concrete of retaining walls.