What is the significance of the 'well development' stage during groundwater monitoring well installation?

The significance of the 'well development' stage during groundwater monitoring well installation is to remove fine-grained particles (silt and clay) introduced into the formation during the drilling process, thereby increasing the hydraulic connection between the well and the surrounding aquifer and ensuring representative groundwater samples are obtained. The drilling process inevitably disturbs the formation around the borehole, creating a 'skin' of reduced permeability due to the compaction and smearing of fine particles. Well development involves agitating the water within the well and then removing the turbid water, carrying away the fine particles. This process is repeated until the water removed from the well is relatively clear and free of sediment. Proper well development is critical for obtaining accurate groundwater level measurements and representative samples for water quality analysis. An improperly developed well can yield samples with artificially high turbidity and contaminant concentrations due to the presence of fine particles, leading to inaccurate assessments of groundwater conditions. It ensures that the water being sampled is truly representative of the aquifer and not influenced by the drilling process. Methods for well development include surging, bailing, and pumping.