What is the maximum percolation rate allowed for the upper 12 inches of soil at the surface in area fill mound systems?

In area fill mound systems, the maximum percolation rate for the upper 12 inches of soil is determined by the soil's ability to absorb water effectively without causing excessive runoff or saturation, which could lead to system failure. A percolation rate of 30 minutes per inch is specified as it indicates a moderate absorption capacity. This allows the wastewater from the mound system to be absorbed adequately by the soil, promoting proper treatment and reducing the risk of groundwater contamination.

Higher percolation rates, such as 15 minutes per inch or 45 minutes per inch, suggest rapid absorption that might not provide sufficient treatment time for the wastewater, while a rate of 60 minutes per inch could indicate a sluggish soil that may lead to saturation issues. Therefore, the 30 minutes per inch standard strikes an optimal balance for efficient wastewater treatment in area fill mound systems.