Large-scale projects, such as new power transmission lines, are characterized by an increased ecological awareness and by a strong public participation in the environmental impact assessment process. Technical criteria, environmental criteria, economical criteria as well as reliability parameters are used to evaluate the impact of the planned transmission line alternatives. For the reliability evaluation a minimal cut-set-algorithm has been implemented, tested and validated with the NEPLANreg reliability tool. The resulting Multi-Criteria Decision Making problem (MCDM), which is solved by a genetic algorithm (GA) in this paper, is to build a reliable transmission grid with low environmental impact on the public sector, minimum on unavailability and with minimal life-time-costs. The results of the optimization process on an example grid are discussed and further improvements are listed.