1. (a) The sizes of members shown in Tables III and IV are the minimum requirements for timber bracing systems used in the sheeting and shoring of excavations.
2. (b) Steel, aluminum or combinations of steel, aluminum and timber bracing systems of equivalent strength and capacity may be used in place of timber bracing systems.
3. (c) Portable, adjustable-type metal shores for trench bracing systems shall be approved.
4. (d) Braces shall be so placed that the full cross-sectional areas required by Tables III and IV of this Subpart bear against the stringers.
5. (e) Stringers shall be placed with their least dimensions flat against the sheeting.
6. (f) Where any side of an excavation is a combination of an unbraced slope in accordance with Table I of this Subpart near the surface and a braced vertical section near the bottom, the sizes of the bracing members shall be determined from Tables III and IV of this Subpart. In such case, the excavation depth shall be the sum of the depth of the braced section plus one-half the depth of the unbraced sloped section.
7. (g) The uppermost brace of any bracing system shall be located not more than two feet below the top of the supported material.

8. (h) The maximum distance between the lowest brace and the bottom of the excavation shall not exceed three feet, except where the sheeting or soldier beam is embedded as stipulated in subdivision (i) below.

   TABLE IV

   MINIMUM SIZES OF STRINGERS AND BRACES

   Wide Trenches—Horizontal Cross-Braces More Than Four Feet But Not Longer Than Eight Feet

   Trench Depth	Type of Soil	Vertical Spacing of Stringers	Horizontal Spacing of Cross–Braces
   4 Feet	6 Feet
   			Stringers	Braces	Stringers	Braces	Stringers	Braces	Stringers	Braces
   5 to 10 ft.	Stiff cohesive	4 ft. max.	4 × 4	4 × 4	6 × 6 or 4 ×8	4 × 6	6 × 6	4 × 6	8 × 8	6 × 6
   	Noncohesive	Over 4 ft. to 6 ft. max.	6 × 6 or 4 ×8	4 × 6	6 × 6	6 × 6	6 × 8	6 × 8	8 × 10	6 × 8
   	Soft cohesive and wet flowing	4 ft. max.	6 × 6	6 × 6	6 × 10	6 × 6	8 × 10	6 × 6	10 × 12	8 × 8
   Over 10 to 20 ft.	Stiff cohesive and noncohesive	4 ft. max.	4 × 6	4 × 6	6 × 6	6 × 6	8 × 8 or 6 ×10	6 × 6	10 × 10	8 × 8
   	Soft cohesive and wet flowing	4 ft. max.	6 × 8	6 × 8	8 × 10	6 × 10	10 × 12	8 × 10	*	*
   Over 20 ft.	For any trench over 20 feet in depth the sheeting, shoring and bracing system shall be designed by a professional engineer licensed to practice in the State of New York. Such design plan, including design analysis and specifications, shall be submitted to the board for special approval before any work is performed on such excavation.

   *

   Sizes of timber for such conditions become excessive. A special structure designed by a professional engineer licensed to practice in the State of New York shall be constructed and used for the specific condition involved.

   Note: Timber sizes are nominal or trade dimensions.

9. (i) If the bottom of the sheeting or soldier beam is embedded below the bottom of the excavation, the maximum distance between the lowest brace and the bottom of the excavation shall not exceed the vertical spacing for braces allowed in Tables III and IV of this Subpart. The minimum depth of embedment of the sheeting or soldier beam shall be three feet. The actual depth of each such embedment shall be such that there is no significant movement of the bottom of the sheeting or soldier beam.

   Exception:

   Where the operation being performed, such as laying large diameter concrete pipe or reinforced concrete culverts, precludes the placing of vertical bracing as specified in subdivisions (h) and (i) above, the vertical spacing may be in accordance with a specific design and plans made by a professional engineer licensed to practice in the State of New York. Such specified bracing system shall be designed so that the sheeting and shoring will withstand all the forces intended to be imposed thereon. Copies of the design and plans of such sheeting and shoring system shall be kept at the job site available for examination by the commissioner.

10. (j) The bracing or shoring of trenches shall be continued as the excavation progresses in length. No person except workmen fabricating the required sheeting and shoring system shall be allowed inside such excavation until the required sheeting and shoring system has been completed.
11. (k) Backfilling and removal of trench supports shall progress together from the bottom of the trench. Jacks or braces shall be released slowly and, in unstable soil, ropes shall be used to remove the jacks or braces from above after employees have vacated the trench.

The use of Tables III and IV shall be subject to the following requirements: