Which soil texture group includes sandy clay, silty clay, and clay?

• A. Soil Group I
• B. Soil Group II
• C. Soil Group III
• D. Soil Group IV

Answer: (B)

The concept here is how soil texture affects drainage and what that means for septic system design. Fine-textured soils, like sandy clay, silty clay, and clay, have small pore spaces and tend to hold water, draining slowly. That slower infiltration makes them more restrictive than sandy or loamy soils, but not the most restrictive soil type. In the common four-group system used for these exams, these clay-rich textures fall into the middle category, which accounts for soils with limited but not completely unsuitable drainage. Soil Group II is the best fit because it reflects slow-to-moderate infiltration typical of clayey textures, signaling that standard drainfield designs may need adjustments or alternatives. The coarser textured groups would include well-drained sands and loams, while the more restrictive groups cover soils with even poorer drainage or other limitations, such as dense clay alone or conditions like perched water tables.