Three sections, six appendices
Subpart P of 29 CFR 1926 has three sections:
- 1926.650: scope, application and definitions
- 1926.651: specific excavation requirements, such as egress and spoil setback
- 1926.652: requirements for protective systems
There is no 1926.653. The trap: after 1926.652 the subpart continues only in Appendices A through F.
The appendices
- A: Soil Classification
- B: Sloping and Benching
- C: Timber Shoring for Trenches
- D: Aluminum Hydraulic Shoring for Trenches
- E: Alternatives to Timber Shoring
- F: Selection of Protective Systems
The trap: Selection of Protective Systems is Appendix F, the last one, not A, B or E.
Trench boxes are shield systems
1926.650(b) states that shield systems include trench boxes. Sloping and benching are the Appendix B methods of cutting back the excavation walls, not a box placed in the trench. Timber shoring is a support system covered by Appendix C, not the definition that names trench boxes.
Which rule lives where
- 1926.651(c)(2): egress in trenches 4 ft or more deep, within 25 ft of lateral travel
- 1926.651(j)(2): excavated material and equipment kept at least 2 ft from the edge
- 1926.652(a)(1): a protective system is required, except in stable rock or under 5 ft deep where a competent person finds no indication of a potential cave-in
- 1926.652(b)(1)(i): unclassified soil sloped no steeper than 1½H:1V
- 1926.652(g)(2): dig no more than 2 ft below the bottom of a shield
The trap: there are two different 2 ft rules. The spoil setback is in 1926.651; the below-shield limit is in 1926.652.
The 20 ft engineer rule is in Appendix B
Sloping or benching for excavations deeper than 20 ft must be designed by a registered professional engineer. That threshold sits in Appendix B, Sloping and Benching, and the tabulated-data limits of Appendices C and D carry it too. The trap: a full-text search of 1926.652 finds no "20 feet", so 1926.652(a)(1) is not the place for it, and neither are the 1926.650(b) definitions.