The report is organised as follows:

• Chapter 1 introduces the function and key characteristics of the geological barrier with regard to long-term safety and site selection. It also summarises why the final stage of site selection focuses on three regions in Northern Switzerland.

• Chapter 2 gives an overview of the geological knowledge base supporting this report, with a special focus on the detailed site investigations carried out in the third and final phase of the site selection process (SGT Stage 3).

• Chapter 3 summarises the regional geological evolution and natural tectonic and climatic processes in the past with a view to understanding the geological barrier as it exists today, as well as its future evolution.

• In Chapter 4 the present-day geological situation in the siting regions is described in detail, with emphasis on the similarities and differences between the regions.

• Chapter 5 focuses on the host rock and the adjacent low-permeability confining units, with a focus on barrier properties and processes ensuring their long-term stability.

• In Chapter 6 scenarios for future geological evolution are developed. These focus on the next one million years and include climate, tectonic and erosion scenarios. Their effects on the geological barrier are discussed.

• Chapter 7 summarises the most important geological findings with regard to site comparison and long-term safety.

Depending on background and interests, the reader may choose different ways to read the report. Besides the classical way of reading a report from front to back or studying specific chapters based on the table of contents, the report structure offers two alternative approaches:

• Track the scientific basis supporting the key geological outcomes for the demonstration of long-term safety and site comparison: Start with the 3-page text summarising the ‘Key outcomes for the demonstration of long-term safety and site comparison’ at the very beginning of the report (English and German versions available). For each statement you will be guided directly to chapters and sections of the report containing the background information necessary to understand and trace the arguments.

• Track the evolution of the database and the key findings in SGT Stage 3 compared to earlier reference studies: Readers who are familiar with past investigation phases and the corresponding geological documentation may start reading with Section 7.1. This section summarises the evolution of the geological database and the related key findings since the demonstration of disposal feasibility for HLW (Entsorgungsnachweis; Nagra 2002) and since the submission of the documentation for Stage 2 of the Sectoral Plan (Nagra 2014h). For each listed bullet point, links to the sections setting out the current state of knowledge are given.

The report describes geological features and processes in varying levels of detail. This is intentional and, for the most part, reflects their importance for safety-relevant aspects or its scientific complexity. Where concepts are not described in the report, to keep the report as succinct as possible, the reader is referred to where further information describing the concept can be accessed.