§ 33.313. Excavations, 10 feet to 15 feet in depth and not more than 42 inches in width.

 (a)  In hard, solid soil, timber shall be used as follows:

   (1)  Uprights. Two by 6 inch planks spaced approximately 4 feet apart center line to center line.

   (2)  Stringers. None.

   (3)  Cross braces. For depths less than 13 feet, three 2 by 6 inch planks, and for depths of 13 to 15 feet, four 2 by 6 inch planks.

 (b)  In soil likely to crack, timber shall be used as follows:

   (1)  Uprights. Two by 6 inch planks spaced 3 feet apart center line to center line.

   (2)  Stringers. Two by 6 inch planks, 3 in the height of the excavations.

   (3)  Cross braces. For depths less than 13 feet, three 2 by 6 inch planks, and for depths of 13 to 15 feet, four 2 by 6 inch planks, cross spaces spaced horizontally not more than 6 feet apart center line to center line.

 (c)  In soft, sandy soil or filled ground, timber shall be used as follows:

   (1)  Uprights. Two by 6 inch close sheeting.

   (2)  Stringers. For depths less than 13 feet, three 4 by 6 inch planks, and for depths of 13 to 15 feet, four 4 by 6 inch planks.

   (3)  Cross braces. Four by 6 inch planks spaced horizontally not more than 6 feet apart.

 (d)  In lieu of one cross brace to each upright, and where the nature of the soil or nearby parallel excavations makes the spacing or uprights closer than 4 feet, they may be held in place by 2 by 6 inch stringers or wales, and cross braces spaced not to exceed 6 feet center line to center line.

   This section cited in 34 Pa. Code §  33.319 (relating to tables).