What is the maximum allowable permeability of soils used for Wisconsin mound installations in the upper 10 inches?

The maximum allowable permeability of soils used for Wisconsin mound installations in the upper 10 inches is categorized as moderately low. This requirement is crucial because it ensures that the soil can adequately filter and absorb effluent from the mound system while preventing rapid drainage that could lead to inadequate treatment or environmental contamination.

Moderately low permeability helps retain effluent long enough for microbial action to occur, which is vital for breaking down organic materials and reducing pathogens. If the permeability were too high, the effluent would flow through the soil too quickly, reducing the time available for these natural processes to occur, potentially leading to soil saturation and failure of the system.

Therefore, the selected category of moderately low permeability supports the efficient operation of the mound system, ensuring it performs effectively while protecting public health and the environment.