Selecting Protective Systems
General Requirements — 1926.652(a)
Under 29 CFR 1926.652(a) and (b), OSHA requires employers to protect employees from cave-ins during excavation work. The standard establishes when protective systems are required and provides options for designing sloping and benching systems.
Employees must be protected from cave-ins by an adequate protective system unless one of the following exceptions applies:
- Stable Rock: The excavation is made entirely in stable rock.
- Excavations Less Than 5 Feet Deep: The excavation is less than 5 feet (1.52 m) deep, and a competent person examines the ground and determines there is no indication of a potential cave-in.
Important: Excavations 5 feet deep or greater generally require cave-in protection, regardless of whether visible signs of instability are present.
Soil conditions can change suddenly due to moisture, vibration, nearby equipment, or the weight of excavated materials. A cave-in can occur without warning, trapping or crushing workers beneath thousands of pounds of soil. OSHA requires cave-in protection at these depths unless the excavation is made entirely in stable rock. For excavations less than 5 feet deep, a competent person must examine the ground and determine that there is no indication of a potential cave-in before workers may enter without a protective system.
Design of Sloping and Benching Systems — 1926.652(b)
The slopes and configurations of sloping and benching systems must be selected and constructed by the employer or his designee in accordance with one of the options below:
Option 1 — Allowable Configurations and Slopes, 1926.652(b)(1)(i): Excavations must be sloped at an angle not steeper than one and one-half horizontal to one vertical (34 degrees measured from the horizontal), unless the employer uses one of the other options listed below.
Option 2 — Appendices A and B 1926.652(b)(2): Determine allowable slopes and benching configurations using OSHA's soil classification requirements in Appendix A and the sloping and benching specifications in Appendix B.
Option 3 — Other Tabulated Data 1926.652(b)(3): Use written engineering tables or charts that identify allowable slopes, configurations, and limitations. The data must identify the registered professional engineer who approved it.
Option 4 — Registered Professional Engineer 1926.652(b)(4): Use a site-specific sloping or benching design approved by a registered professional engineer. The written design must identify safe slopes, configurations, and the approving engineer.
For Options 3 and 4, the required documentation must be maintained at the jobsite during construction of the protective system.
Design of Other Protective Systems — OSHA 29 CFR 1926.652(c)
Although paragraph (b) addresses only sloping and benching, 1926.652(a) also permits protective systems designed under paragraph (c), including shoring, trench boxes, and other support or shield systems.
These systems also have four design options under 1926.652(c): OSHA appendices, manufacturer's tabulated data, other approved tabulated data, or a registered professional engineer's design.
Option 1 — Designs Using Appendices A, C, and D: Timber shoring designs must follow Appendices A and C. Aluminum hydraulic shoring must follow the manufacturer's tabulated data under Option 2, or Appendix D when that data cannot be used.
Option 2 — Designs Using Manufacturer's Tabulated Data: Protective systems may be selected and constructed according to the manufacturer's tabulated data, including specifications, recommendations, and limitations.
Option 3 — Designs Using Other Tabulated Data: Protective systems may be designed using other tabulated data, such as tables and charts approved by a registered professional engineer.
Option 4 — Designs by a Registered Professional Engineer: Protective systems may be designed by a registered professional engineer using site-specific engineering calculations and specifications.
OSHA 1926 Subpart P Appendix F is a summary for excavations 20 feet or less in depth. Where the working area of an excavation is constantly moving, as in laying a conduit, shield systems or trench boxes may be the more appropriate protective devices to use.
Excavations Greater Than 20 Feet in Depth
Protective systems for use in excavations more than 20 feet in depth must be designed by a registered professional engineer in accordance with OSHA 1926.652(b) and (c).
Knowledge Check Choose the best answer for the question.
4-7. Under OSHA 1926.652(a), at what excavation depth is cave-in protection generally required, regardless of visible signs of instability?
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