All simple benched excavations 20 feet or less in depth must have which of the following?

In the context of excavation safety, particularly for simple benched excavations that are 20 feet or less in depth, maintaining proper slope ratios is critical to prevent collapses and ensure worker safety. The correct option states that these excavations must have a maximum slope of 3/4:1.

This means that for every ¾ unit of horizontal distance, there can be a 1 unit increase in vertical distance. This slope ratio is generally recommended for excavations of lesser depth—up to 20 feet—because it helps provide stability to the excavated area and reduce the risk of soil failure. A slope of 3/4:1 provides a balance between maximizing excavation depth and minimizing potential hazards associated with steeper slopes, which can lead to increased pressure on the soil and a higher likelihood of collapse.

Understanding the significance of slope ratios in excavation work is vital; they allow for safe access and egress for workers and minimize the risk of incidents. In situations where the excavation depth increases or in certain soil types, different slope specifications may apply, thus highlighting why this particular ratio is sufficient for shallow excavations.