This report discusses in detail the necessary prerequisites, processes involved and applicability of ‘non-intervention’ as a strategy for dealing with radioactive contamination. Particular emphasis is placed on modelling tools as an integral element of monitored natural attenuation (MNA). It provides a comprehensive critique of the applicability of MNA and explores its limits. While MNA is de facto relied upon in many instances where a contamination cannot be completely removed to an engineered repository, it is emphasized that ’non-intervention’ is not equivalent to a ‘do nothing’ option. In order to rely on MNA safely, a thorough understanding of the site and the migration behaviour of the contaminants in the given environment is needed, which is gained by a comprehensive site investigation. This report complements other recent reports on remediation techniques and strategies with a less invasive concept.