What is the purpose of purging before collecting groundwater samples?

The purpose of purging before collecting groundwater samples is to remove stagnant water and obtain a more representative sample. This is essential because groundwater wells can contain water that has been sitting stagnant in the well casing or the surrounding aquifer for extended periods. This stagnant water may not accurately reflect the current conditions of the groundwater due to factors such as the influence of surface water, changes in water quality, or the presence of contaminants.

By purging the well, technicians can draw out this stagnant water, which allows for the collection of fresh water that is more indicative of the overall groundwater quality and conditions. This practice ensures that the sample taken is representative of the water currently present in the aquifer, rather than what may be biased due to prior water that has not moved or mixed effectively with the surrounding water.

The other choices do not align with the primary goal of purging. For example, ensuring proper well casing installation relates to well construction standards rather than sampling process. Increasing water levels in the well is not a goal of purging; rather, purging is about achieving a more accurate sample for analysis. Lastly, while purging does indirectly help check for contamination by obtaining a fresh sample, that is not the primary purpose of the purging process itself.