What is the minimum vertical separation requirement for intermittent sand filters used in certain soil types?

The minimum vertical separation requirement for intermittent sand filters in certain soil types is established to ensure proper treatment of wastewater and to protect groundwater from contamination. A separation of 12 inches is typically designated because it allows sufficient space for the treatment process to occur effectively. This distance minimizes the risk of contaminants leaching directly into the groundwater and allows for adequate filtration and absorption of effluents before they reach the saturated zone of the soil.

Choosing a separation that is too shallow may not provide enough time for microorganisms in the soil to break down contaminants, leading to potential environmental hazards. While greater separation distances may be beneficial in some contexts, the 12-inch requirement strikes a balance between effective wastewater treatment and the practicalities of installation and site constraints, particularly in soils that are more permeable. In essence, this specification helps maintain public health standards and protects local water resources.