The present report has been written to show the feasibility of construction and the operational suitability of different intermediate and final storage concepts for high-level radioactive wastes. It summarizes the information from a project study given under contract by Nagra. The report should orient a broader public about the possible construction of such intermediate and final repositories. The work presented here refers to radioactive wastes which need an extremely long isolation time. Important information from a separate study concerning different aspects of the drilling of deep boreholes, has been integrated into the present report.