When is it good practice to bench the underlying soil?

• A. When the slope of the site is between 0% and 5%
• B. When the slope of the site is between 5% and 10%
• C. When the slope of the site is between 10% and 25%
• D. When the slope of the site is greater than 25%

Answer: (C)

Benching is a safety and stability technique used when digging on sloped ground. By cutting the slope into horizontal steps, you create stable, level surfaces that help prevent the soil from sliding into the trench or bed and provide a solid base for installation.

On slopes in the 10% to 25% range, the soil is prone to movement but isn’t so steep that stabilization isn’t feasible. Benching reduces the driving forces that could cause a mass failure, makes it easier to level the trench bottom, and improves safety for workers and the integrity of the installation. On gentle slopes (0–5% or 5–10%), the ground is typically stable enough that benching isn’t necessary. On very steep slopes (greater than 25%), benching may not be sufficient by itself, and other stabilization methods or redesign of the site may be required.