Excavation — Soil Classification (Hands-On)

Talking points

1. The competent person must classify soil as Type A (most stable), Type B, Type C (least stable), or stable rock. Classification determines the required protective system.
2. Visual tests: look for cracks or fissures in the excavation walls, water seepage, layers of sand or gravel, evidence of previous backfill, and signs of vibration damage.
3. Thumb penetration test: if you can easily press your thumb into the soil, it is likely Type C. If it takes considerable pressure, it may be Type A or B.
4. The pocket penetrometer provides a quantitative reading. Type A requires unconfined compressive strength above 1.5 tsf; Type B is 0.5-1.5 tsf; Type C is below 0.5 tsf.
5. If any condition suggests the soil is weaker than initially classified — water seepage, vibration, recent rain, or mixed soil layers — reclassify to the weaker type.

Ask the crew

What type of soil are we working in today — and how was it classified? Can the competent person walk us through the test they performed?

Standards this talk is built on

• 29 CFR 1926 Appendix A

A toolbox talk is a short safety briefing. It supports the training a standard requires; it does not replace it.

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