Which types of soil are typically not suitable for sewage disposal by subsurface?

Which types of soil are typically not suitable for sewage disposal by subsurface?

• A. Sand and gravel
• B. Silt and clay
• C. Clay and clay-loam
• D. Gravel and loam

Answer: (C)

The types of soil that are typically not suitable for sewage disposal by subsurface means are those that are heavy and slow-draining, which is characteristic of clay and clay-loam soils. These soils have very low permeability, meaning they do not allow for efficient drainage or filtration of wastewater. This can lead to a higher risk of surface water contamination, as the sewage cannot effectively percolate through the soil layers and break down properly. In contrast, soils such as sand and gravel are highly permeable, allowing sewage to flow through and be naturally filtered. Silt and clay, while having some drainage capabilities, also exhibit higher levels of retention, but do not pose the same level of risk as the denser clay soils. Gravel and loam generally allow for better drainage and are typically considered suitable for subsurface sewage disposal. Thus, the reason clay and clay-loam soils are unsuitable relates to their physical properties that impede the movement and treatment of wastewater, reinforcing the importance of suitable soil types for effective sewage management.

The types of soil that are typically not suitable for sewage disposal by subsurface means are those that are heavy and slow-draining, which is characteristic of clay and clay-loam soils. These soils have very low permeability, meaning they do not allow for efficient drainage or filtration of wastewater. This can lead to a higher risk of surface water contamination, as the sewage cannot effectively percolate through the soil layers and break down properly.

In contrast, soils such as sand and gravel are highly permeable, allowing sewage to flow through and be naturally filtered. Silt and clay, while having some drainage capabilities, also exhibit higher levels of retention, but do not pose the same level of risk as the denser clay soils. Gravel and loam generally allow for better drainage and are typically considered suitable for subsurface sewage disposal.

Thus, the reason clay and clay-loam soils are unsuitable relates to their physical properties that impede the movement and treatment of wastewater, reinforcing the importance of suitable soil types for effective sewage management.