For excavations in Type A soil, the maximum allowable slope depends on the depth and duration the excavation is open. For simple slope excavations 20 feet or less in depth, the maximum allowable slope is 3/4:1 (horizontal to vertical) 1, 2. However, if the excavation is open for 24 hours or less (short term) and is 12 feet or less in depth, a maximum allowable slope of 1/2:1 is permitted 1, 2.

It's important to note that surcharge loads from stored material, equipment, or traffic can affect the required slope. A competent person must determine how much the slope needs to be reduced below the maximum allowable slope in such cases 5, 20.