1. Provision for stability of slopes is one of the main problems in designing plains PSHS. 2. The reasons for occurrence and a “chain reaction” of development of landslide phenomena on the south slope of the area of basic structures of the Zagorsk PSHS were peculiarities of its engineering-geological structure that were not properly taken into account in designing and carrying out construction work. 3. For the purpose of stabilizing the landslide slope, a system of engineering measures was developed and implemented, including a change in the configuration and structure of the right-bank abutment of the upper-basin levee to the water intake, construction of a banquette, filling of a counterbanquette, draining of moraine loams, grading of the slope, surface water diversion, and monitoring of the state of the slope and elements of the antilandslide protection. 4. Data from full-scale observatins indicate the effectiveness of the antilandslide measures that were performed and a state of the slope corresponding to criteria for the hydro development's safe operation. 5. Innovative elements of the system of measures to stabilize the south landslide slope of the Zagorsk PSHS are: the complex nature of measures, providing for the optimum set of criteria with respect to reliability, technological efficiency, construction time, and cost of adjusted expenditures; minimization of one-time and total excavation for the banquette, providing for the least disruption of the slope in the process of construction; draining of moraine loams, which has no known analog; the use of an ejector unwatering system, which provides for minimum adjusted expenditures on construction and operation of the drainage system.