What is the most important factor used to determine the number of samples to be collected?

The purpose for the sampling is indeed the most significant factor in determining the number of samples to be collected. This is because the objectives of the sampling dictate the necessary frequency and volume of samples needed to achieve reliable and representative data.

For instance, if the purpose is compliance monitoring, the number of samples may need to align with regulatory requirements that specify how often sampling should occur to ensure that discharge limits are being met consistently. Conversely, if the goal is for a study or research project, the sampling strategy may require more frequent or more extensive sampling to accurately capture variability or trends over time.

Understanding the aim behind the sampling allows inspectors to assess what data is essential, identify patterns, and determine whether the observed levels of contaminants are transient or persistent. This strategic approach ensures that the sampling is not only effective but also efficient, providing the necessary insight while minimizing unnecessary costs or efforts.