What is the primary factor in determining the configuration of a mound system?

The depth of unsaturated soil is the primary factor in determining the configuration of a mound system because it directly influences the design and placement of the mound. Mound systems are used to treat wastewater in areas where the soil's natural drainage capabilities are limited, particularly when the groundwater level is high or the native soil has poor percolation rates.

A thorough assessment of the depth of unsaturated soil helps determine how much soil is available for wastewater treatment before it reaches the groundwater. If the unsaturated zone is too shallow, the wastewater may not be adequately treated before it can contaminate groundwater. This knowledge is critical to ensure that the mound can function effectively and safely.

Factors like the slope of the site, the size of the infiltration bed, and the shape of the mound are important for overall site suitability and performance but do not fundamentally alter the type of mound system needed in relation to the unsaturated soil depth. Thus, the depth of unsaturated soil is the most critical consideration in determining how the mound system will be configured, ensuring appropriate treatment of wastewater before it percolates into the underlying soils or groundwater.