6.9. At the stage of site investigation and site selection, the safety case should support the process leading to the identification of one or more potential disposal sites and should assist in the progression to the next step of development. The safety case and its content will evolve as the project develops in terms of engineering and in terms of characterization of the different natural and engineered components of the disposal system. At this stage, the safety assessment is initially generic in nature, but will evolve as the design develops and the level of detail of the site characterization increases. Criteria for rejecting a site and desirable characteristics for a site should be determined at this stage; the site characterization should be such that it is possible to verify whether the desirable characteristics are present or to determine whether the site should be rejected when compared to the criteria.