4.9. The general objective of monitoring programmes during the pre-operational period is to establish a baseline of pre-existing levels of contaminants, to enable evaluation of the impact of the waste disposal system and to identify parameters that may be indicative of performance in the post-closure period. Site characterization programmes (as conducted in the pre-operational period) typically establish natural characteristics of features, events, and processes occurring in the environment of the disposal facility (e.g. water table fluctuations) that may significantly influence the design and subsequent short term performance (i.e. in the operational period) and long term performance (in the post-closure period) of the facility. In this regard, the monitoring programme should be closely integrated with the safety case and supporting safety assessment and with procedures for construction and operation. The baseline should be developed to allow the identification of trends. The baseline should also enable the impact of the facility as it evolves over time to be discerned; this information can then be used to update the safety case.