Refer to the figure: A is equal to a 25` (may be 20`) maximum height in a simple trench. In type “C” soil, according to OSHA, what is the maximum allowed slope of “C”?

Refer to the figure: A is equal to a 25` (may be 20`) maximum height in a simple trench. In type “C” soil, according to OSHA, what is the maximum allowed slope of “C”?