6.5. Baseline monitoring is concerned with measurement of the initial values of parameters that will continue to be monitored by either continuous or periodic observations. The scope of baseline monitoring includes the determination of conditions and parameters of potential interest for the understanding of basic earth science, engineering and the environment, and for informing the operational safety assessment and the post-closure safety assessment for the disposal facility. For example, baseline monitoring is used to evaluate changes that occur in the rock and the groundwater system during the construction and operational periods and, at the post-closure stage, to evaluate any significant impacts that the presence of the disposal facility may have on natural processes and the environment. In practice, the monitoring programme will begin during the site investigation stage. A more comprehensive description of establishing baseline conditions can be found in Ref. [18].