In a site evaluation, why is the zone of saturation relevant?

The zone of saturation is crucial in site evaluations for onsite wastewater systems because it directly influences the risk of groundwater contamination. When the wastewater system, such as a septic tank or drain field, is improperly situated with respect to the zone of saturation, there is a potential for effluent to enter the saturated layer of soil and subsequently contaminate nearby groundwater sources. This is particularly relevant in areas with high water tables, where the saturated zone can be close to the surface. Ensuring that the wastewater treatment system is designed to function above the zone of saturation helps to mitigate the risk of pollutants leaching into groundwater, protecting human health and the environment.

Understanding how the zone of saturation operates in relation to onsite wastewater systems is essential for effective system design and placement. While other factors like vegetation and soil texture may be influenced by the zone of saturation, they are secondary to the immediate concern of groundwater contamination. Hence, the impact on groundwater contamination risk is the primary reason why the zone of saturation is a critical consideration in site evaluations.