Certified Erosion, Sediment, & StormWater Inspectors (CESSWI) Practice Test 2026 - Free CESSWI Practice Questions and Study Guide

The A layer, often referred to as topsoil, is the uppermost layer of soil where a significant amount of biological activity occurs. This layer is rich in organic matter, nutrients, and microorganisms, all of which are essential for plant growth. It is darker in color compared to the layers below it due to the presence of decomposed organic material. The A layer provides vital support for vegetation, making it crucial for agricultural practices and natural ecosystems.

In contrast, the other layers—B, C, and D—serve different functions and characteristics. The B layer, typically known as subsoil, contains less organic matter and is more mineral-rich, while C layer consists of weathered rock and unconsolidated materials. The D layer, often referred to as bedrock, is the deepest layer and consists of solid rock that hasn’t undergone significant weathering. Understanding these different soil layers is important for managing erosion and sediment control effectively.