Where should soil samples be collected in relation to the water table?

Collecting soil samples at the approximate top of the water table is essential for accurately assessing potential contamination. This location is significant because it allows for the examination of the soil that is potentially influenced by the groundwater. Contaminants often migrate from the soil into the groundwater, making the soil at the top of the water table a critical zone for detection.

Sampling at this level helps to identify the concentration of contaminants that could be leaching into the groundwater, thereby providing valuable data for risk assessment and remediation planning. By focusing on the area just above the water table, analysts can ideally evaluate the interaction between the soil and groundwater, which is vital for understanding the environmental impact of any contaminants that may be present.

While other options suggest sampling at various depths, they either miss the opportunity to capture the influence of the saturation point on contaminant migration or may not provide the most relevant data needed for effective site assessment.