How much separation must be maintained from the proposed trench bottom and the seasonal high water table or restrictive layer, unless an advanced treatment system is used?

The requirement for maintaining a separation distance from the bottom of a proposed trench to the seasonal high water table or restrictive layer is critical in soil absorption systems. A separation of 2 feet is essential to ensure that there is adequate space for wastewater to be treated by the soil and to prevent contamination of the groundwater.

This 2-foot separation is established based on considerations of effluent movement, soil characteristics, and the functioning of the absorption system. It allows for sufficient soil volume to filter and biologically treat the effluent before it reaches the groundwater or any restrictive layers, such as bedrock or compacted soil layers. Furthermore, this separation helps to mitigate the risk of saturation and waterlogging in the absorption trench, which could impede the performance of the system and lead to system failure.

Using an advanced treatment system may alter these requirements, often allowing for reduced separation, but in the absence of such systems, adhering to the 2-foot guideline is crucial for effective and safe wastewater management in Wisconsin mound systems.