For a clay soil condition, what is the required separation from the trench bottom to a wetness condition?

For clay soil conditions, the required separation from the bottom of a trench to a wetness condition is 36 inches. This requirement is essential because clay soils have low permeability, which means they do not drain well. High water tables in these conditions can lead to saturated soils that affect the functioning of septic systems and ultimately result in failure or poor effluent quality.

The 36-inch separation ensures that there is adequate space for the effluent to disperse without being impeded by groundwater or saturated soil conditions. This distance allows for proper treatment of the wastewater as it passes through the soil, which is critical in preventing contamination of groundwater and protecting public health.

In addition, the requirement recognizes that different soil types have different characteristics regarding drainage and water retention. Clay, with its tendency to hold water, necessitates a greater distance to maintain the effectiveness of the septic system. It contributes to long-term operational sustainability by reducing the risk of system overload from wetness and enabling effective soil absorption and filtration.