Which of the following classes of soil is NOT considered suitable for standard systems?

Soils are categorized into classes based on their characteristics, which influence how well they drain and their ability to support traditional septic systems. Class 1a and Class 1b soils typically exhibit excellent drainage capabilities and are well-suited for standard systems, as they allow for adequate effluent dispersion and microbial activity.

Class 2 soils also demonstrate reasonable drainage but may have some limitations compared to Class 1, making them suitable for standard systems with proper management. Conversely, Class 3 soils have moderate to poor drainage qualities, often characterized by high clay content or a significant presence of restrictive layers. These factors make Class 3 soils problematic for standard systems, as they can lead to insufficient effluent treatment and greater risk of system failure. Thus, Class 3 is not considered suitable for standard septic systems, which rely heavily on adequate percolation and drainage to function correctly.