What is a restrictive horizon?

A restrictive horizon refers to a specific layer within the soil profile that has characteristics capable of slowing down or impeding the movement of groundwater. This can occur due to various properties, such as compaction, low porosity, or the presence of clay minerals that restrict water flow. Identifying such a horizon is crucial when evaluating soil for onsite wastewater systems, as it can affect the drainage capacity and overall efficiency of the system.

The presence of a restrictive horizon can lead to increased risks of groundwater contamination and can necessitate specific design modifications to wastewater systems to ensure environmental protection and compliance with regulations. Understanding this concept is fundamental for professionals working with onsite wastewater systems, ensuring they assess soil layers effectively to determine suitability for such systems.

The incorrect options, while relevant in soil science, do not accurately reflect the definition of a restrictive horizon. For instance, a layer that promotes water movement signifies good drainage properties, which contradicts the concept of a restrictive horizon. Similarly, a layer rich in organic materials or a surface layer exposed to the atmosphere describes other characteristics of soil that are unrelated to the movement of groundwater and do not function as barriers to it.