Type C soils include which of the following descriptions?

• A. Clay
• B. Silt
• C. Sands and gravels and anything with water freely seeping or submerged
• D. Organic peat

Answer: (C)

Type C soils are the least stable for excavation and trenching. They’re the granular soils—sands and gravels—especially when loose, and any soil that has water freely seeping through or is submerged. Water lowers the effective stress and the shear strength, making these soils prone to flow or cave-ins, so they require the most cautious protective measures. That description—sands and gravels and anything with water freely seeping or submerged—best fits Type C. Clay and silt tend to be cohesive and are classified differently, while organic peat is highly unstable and not typical of Type C in standard classifications.