Trench Sloping Calculator: OSHA 1926.652 Soil Type Slope Ratios

How It Works

1. Start with Competent-Person Soil Classification

   Select the soil type already determined on site. The app does not perform Appendix A visual/manual tests or downgrade for water, vibration, surcharge, layering, or prior disturbance.

2. Enter Trench Dimensions

   Input bottom width, depth, and length. Trenches over 20 feet require a registered professional engineer design, and protective-system decisions remain outside this geometry calculator.

3. Review the Appendix B Geometry Prompt

   The calculator applies the selected slope ratio to estimate top width, slope run, and trapezoidal excavation volume for planning review.

4. Review Spoil, Bedding, and Egress Prompts

   Check loose spoil volume, 2-ft spoil setback reminder, the simplified OD+12 in pipe-bedding prompt, and the 4-ft egress threshold.

5. Resolve Field Reliance Gaps

   Use the output as a planning aid only, then verify with the competent person, current OSHA/state-plan rules, site conditions, utilities, water, surcharge loads, and PE review where required.

Built For

• Estimators screening excavation geometry and spoil quantities before site-specific review
• Competent persons checking whether entered dimensions need additional protective-system review
• Site supervisors comparing footprint prompts against available right-of-way before final excavation planning
• Civil contractors estimating cubic yards for early sewer or utility trench planning
• Safety teams documenting source warnings and unresolved field-reliance gaps before excavation review
• Municipal crews comparing preliminary open-cut geometry along a route with varying field conditions
• Project teams flagging egress, spoil, bedding, and PE-review questions before work planning

Features & Capabilities

Appendix B Slope Prompt

Uses the selected Type A, Type B, Type C, or stable-rock prompt to show the slope ratio and angle. Soil classification remains a competent-person field decision.

Top Width Calculation

Screens top width from depth and selected slope ratio so the excavation footprint can be reviewed before field reliance.

Excavation Volume Output

Computes trapezoidal excavation volume and loose spoil planning estimates for early hauling review.

SVG Cross-Section Diagram

Generates a visual cross-section showing the trench profile with labeled dimensions, slope angle, and bottom width.

Spoil & Bedding Estimates

Loose spoil volume with selectable swell factor, truck-load estimate, OSHA 2-ft spoil setback reminder, and a simplified pipe-bedding volume prompt.

PDF Export

Export trench diagrams, source warnings, residual gaps, and calculation prompts for planning review.

Assumptions

• Maximum allowable slopes per OSHA 29 CFR 1926.652 Appendix B: Type A = 3/4:1 (53 degrees), Type B = 1:1 (45 degrees), Type C = 1.5:1 (34 degrees)
• Stable Rock permits vertical excavation with no sloping requirement per OSHA Appendix B
• Soil classification is user-selected; OSHA Appendix A visual/manual tests and downgrade conditions must be handled by the competent person
• Trench profile assumes uniform soil type from surface to bottom - layered soils use the weakest layer classification
• Excavation volume calculation uses a trapezoidal cross-section with uniform slope on both sides
• Benching, shoring, shielding, and protective-system selection are outside this sloping/volume screen
• Protective-system requirements must be verified against current OSHA/state-plan rules and competent-person findings

Limitations

• Does not account for surcharge loads (spoil piles, construction equipment, traffic) near the trench edge, which require additional setback or flatter slopes
• Groundwater, seepage, and dewatering conditions change soil classification - saturated soil defaults to Type C regardless of dry classification
• Does not model mixed soil layers where different strata require different slope angles within the same excavation
• Cannot replace daily field inspections by a competent person, which are required by OSHA after rain, freeze/thaw, and vibration events
• Trenches deeper than 20 feet require registered professional engineer design; this calculator remains a planning screen only
• Adjacent structures, underground utilities, and vibration from nearby traffic may require flatter slopes than the OSHA maximum allowable values

References

• OSHA 29 CFR 1926.652 - Requirements for Protective Systems in Excavations
• OSHA 29 CFR 1926.652 Appendix A - Soil Classification (visual and manual test procedures)
• OSHA 29 CFR 1926.652 Appendix B - Sloping and Benching (maximum allowable slopes by soil type)
• OSHA 29 CFR 1926.651 - Specific Excavation Requirements (competent person, inspections, access)
• OSHA Publication 2226 - Excavation: Hazard Recognition in Trenching and Shoring
• NIOSH Workplace Solutions - Preventing Worker Deaths and Injuries from Excavation Cave-Ins (Publication No. 2015-108)

Frequently Asked Questions