Pre-project geoecological studies were carried out in autumn 2015 along the entire length of the Tikhomandritsa river, in Navolok lake waters near the river source and Udomlya lake near its mouth, as well as on the territory adjacent to the river, as part of the Comprehensive Engineering Surveys. The aim of the studies was to obtain initial data to assess the current ambient conditions of the study area, as well as to develop the project of cleaning the upper stretch of the Tikhomandritsa riverbed and spillway structure construction. Water, bottom sediments and soil contamination levels were identified. It is found that the water quality in the studied water bodies belongs to the contaminated category. Bottom sediments at the upper stretch of the river up to a distance of 2.5 km from its source are pure and can be used in agriculture without restrictions. Bottom sediments samples taken at a distance of 5.5 km from the river source and its mouth contain dangerous level of coliform bacteria. Basing on the territory survey a tree and shurberry felling plan was drawn up and the volume of works of the river purification was determined. The project implementation will help to increase the river flow in dry water years, increase its self-cleaning velocity and environmental improvement of the area. In addition, the increase of water flow into Udomlya lake will provide Kalinin NPP with additional water resources for its process water supply. The conceptual scheme of this study is largely applicable for the basins of other small rivers
