907.08 UNSUPPORTED SIDES AND FACES.

   The sides or exposed faces of excavations made in rock may be unsupported except when the following conditions obtain:

   (a)    The sides or exposed faces are composed of loose, shattered, faulted or disintegrated rock and/or pockets of clay or other soil, any or all of which are so extensive and/or of such character as to endanger the lives of, or subject to possible injury, the employees or workmen in or near or required to be in or near the excavation.

   (b)    The rock is seamed and such seams lie at an angle of 30° or more with the horizontal and are filled with clay or other material upon which the rock might slide.

   (c)    In shale excavations, if, within the duration of the work, the shale tends to disintegrate. (Ord. 5138. Passed 9-20-50.)