What are the soil requirements for leaching chambers or gravelless pipe systems after a septic tank?

The correct choice reflects the specific soil requirements necessary for the effective operation of leaching chambers or gravelless pipe systems following a septic tank. These systems rely on the characteristics of the soil to properly filter out contaminants and promote the appropriate percolation of effluent.

Well-drained Class Ib, II, or III soils are essential because they provide the optimal balance of drainage and absorption capacity for the effluent. Class I soils have the most favorable drainage capabilities, while Class II and III soils still maintain adequate drainage with some limitations. The recommendation of 2 feet ensures that the effluent has enough soil to filter through, allowing for the proper treatment of wastewater before reaching the groundwater.

In contrast, the other options present scenarios that would either offer insufficient absorption, can lead to pooling or backup issues, or are composed of materials not conducive to effective drainage and leaching of wastewater. Sandy soil might not retain enough moisture or nutrients for effective biological treatment, clay soil can lead to inadequate drainage and slow percolation, and organic material might decompose and create blockages rather than facilitate effective leaching. Therefore, the specified depth and type of soil in the correct answer are crucial for maintaining the functionality and longevity of the leaching systems.