A sample for physical and chemical analysis of a new well must be taken after how many hours of continuous pumping?

The requirement to take a sample for physical and chemical analysis of a new well after 36 hours of continuous pumping is based on the need for stabilization of the water quality and aquifer characteristics. Continuous pumping for this duration allows the well to draw water from the surrounding aquifer, effectively flushing out any stagnant water within the well casing and ensuring that the sample reflects the true conditions of the water supply.

This time frame is crucial because it permits the well to reach a steady state where the water being extracted is representative of the aquifer's long-term water quality. Sampling too early may yield results that are influenced by transient conditions or residual water that hasn't yet been fully replaced by fresh groundwater. After 36 hours of pumping, the likelihood of obtaining a reliable sample that accurately represents the well's water quality significantly increases, making it the appropriate timeline for conducting the analysis.

The other durations provided are incorrect as they either allow insufficient time for stabilization (such as 12 hours) or exceed the typical recommendations without added benefits (like 48 hours), which is generally unnecessary for routine testing once stability has been established.