Which of the following is not a basis to demonstrate final stabilization?

• A. % impermeability
• B. Vegetative cover percentage
• C. Absence of bare soil
• D. Soil surface crust formation

Answer: (C)

Final stabilization means the disturbed area has a durable, protective surface that greatly reduces erosion risk over the long term. The most direct ways to show that are through a sufficient vegetative cover, or surface conditions that provide lasting protection.

Vegetative cover percentage is a primary indicator because living plants create a canopy and root network that guard the soil from raindrop impact, reduce runoff, and bind the soil. A measured cover level reflects that protection is actually in place.

Soil surface crust formation is another recognized indicator since a stable crust can resist erosion by deterring detachment of soil particles under rainfall and overland flow. It shows the surface has developed a durable protective layer.

Percent impermeability is also relevant because surfaces that become effectively impermeable to water can limit the detachment and transport of soil by runoff, contributing to a stabilized surface.

Absence of bare soil, while intuitively suggesting some protection, is not a reliable stand-alone basis for final stabilization. It’s possible to have no bare soil but still lack adequate protective cover (for example, a crust that flakes, or non-vegetative material that doesn’t protect against erosion) or to misinterpret short-term conditions. Therefore, it’s not treated as a sole criterion for demonstrating final stabilization.