Assessment of the impact of a large infrastructure investment on the natural and social environment is an art which, although codified in legal regulations, remains largely the domain of difficult knowledge from many technical, natural and social disciplines, as well as law and economy. The ultimate goal should be to convince the decision-making public administrator that the variant of the implementation of the infrastructure project proposed by the investor is the best possible, and that the conflicts it causes with the natural and social environment have been minimized by the selection of appropriate technical and organizational measures, and are therefore acceptable. The possibility of making a decision on environmental conditions depends on the extent to which the EIA report prepared for this investment convinces the decision-making regional director of the WWTP that an optimal solution has been proposed from the point of view of functional, technical and environmental criteria. Choosing by the investor several variants of the railway line routing may be accepted. Better assessment of the impact on the social environment becomes possible when data is available on the number of demolitions and the number of people in the impact zone of the planned line and the ailments it will be exposed to.