For a 9-foot deep excavation in cohesive, type B soil, what is the correct sequence of benching profile?

The correct choice emphasizes a safe and effective method for benching when working in cohesive, type B soil, particularly at a depth of 9 feet. The profile of 3v:6h for the first step denotes that for every 3 units of vertical height, the bench extends horizontally 6 units. This configuration provides a gentler slope, which is particularly important for stability when excavations reach depths where soil cohesion may be a factor, reducing the likelihood of collapse.

Following this, the second step utilizes a 3v:3h ratio to create a more pronounced vertical height while maintaining some horizontal support. These ratios comply with safety regulations and best practices for benching in such soil conditions, allowing workers to operate safely within the excavation.

This sequence ensures that workers have a safe working platform while minimizing the risk of soil movement or failure, which is especially crucial in cohesive soils that may behave differently under load. Proper benching also aids in allowing easier access to the excavation site for equipment and personnel, promoting overall safety and efficiency.