Also in: Disaster Response and Recovery
Excavation Slope and Bench-Step Plan
OSHA Appendix B slope ratios A 0.75:1 / B 1:1 / C 1.5:1 turned into spoil volume (yd^3), surface footprint.
Example
You enter
- Trench depth (ft) 8
- Soil class (OSHA Appendix B) B
- Surcharge load near trench false
- Excavation length (ft) 50
- Bottom width (ft; default 2) 2
You get
- Top width (ft) 18
- Spoil volume (yd^3) 148.2
- Surface footprint (ft^2) 900
Checked against published worked examples from: OSHA.
Details, formula, and sources
ScopeOSHA Appendix B slope ratios A 0.75:1 / B 1:1 / C 1.5:1 turned into spoil volume (yd^3), surface footprint, and bench-step layout. Competent person on-site governs the final plan.
Formula or tablehorizontal_offset = depth * ratio (A 0.75 / B 1.0 / C 1.5). top_width = bottom_width + 2 * offset. cross_section = (top + bottom) / 2 * depth. volume_yd3 = cross_section * length / 27. Bench layout (A/B): 4 ft per bench; horizontal_step = bench_height * ratio.
Source and editionOSHA 29 CFR 1926 Subpart P Appendix B and §1926.652.
Free accessecfr.gov.
What governsMath aid for personal verification. Stop work and consult the qualified person on site if any number does not match the field condition.
API field namesdepth_ft, soil_class, surcharge, length_ft, bottom_width_ft, top_width_ft, spoil_volume_yd3, footprint_ft2
- Soil classes A 0.75:1, B 1:1, C 1.5:1OSHA Subpart P Appendix B
- Bench height 4 ft typicalOSHA Subpart P engineering practice
- Surcharge bump +0.25 H:V additive when surcharge load presentengineering practice
- Bottom width default 2 ft (utility-trench common case)engineering practice
- Depth ceiling above 20 ft requires PE design per 1926.652(b)(4); tile stops thereOSHA 1926.652(b)(4)