What is the percolation rate requirement for the upper 12 inches of soil profile in Area Fill mounds?

The percolation rate requirement for the upper 12 inches of the soil profile in Area Fill mounds being set at 30 minutes per inch or faster is essential for ensuring proper drainage and effectiveness of the soil absorption system. A percolation rate of 30 minutes per inch indicates that the soil can effectively transmit water, allowing effluent from the system to be absorbed and not pooling on the surface or backing up in the system.

This timeframe balances the need for sufficient drainage while also ensuring that the soil can retain enough moisture to facilitate biological treatment of the effluent. If the percolation rate were slower (longer than 30 minutes per inch), it would hinder the system's ability to perform efficiently, potentially leading to saturated conditions that could affect the system's overall function and create issues such as odor, system failure, or environmental contamination. Thus, maintaining this percolation rate is crucial for the successful operation of Area Fill mound systems.