Geotechnical Reports & Soil Borings
Before a building, road or utility is built, engineers often study the ground. A geotechnical report records what lies below the surface and how it will behave. For excavation crews, it is a map of what could go wrong underground.
- Excavation Crews
- Competent Persons
- Supervisors
What is in the report
- Soil borings and test pits: logs showing layers of soil and rock at each location, with depth.
- Soil properties: strength, density, moisture and classification. See Soil Classification and Soil Tests.
- Groundwater: depth of the water table and seasonal changes. See Dewatering.
- Bearing capacity and settlement estimates for foundations.
- Recommendations for excavation slopes, shoring, backfill, compaction, pavement and foundations.
- Hazards such as fill, organic soils, expansive clay, sinkholes or contamination. See Sinkholes & Voids and Contaminated Soil.
Why crews should see it
- A competent person must classify soil and choose protective systems for trenches. The report gives useful information, but daily on-site inspection is still required. See Competent Person Inspections.
- It shows where water or soft ground may cause cave-ins or make equipment unstable.
- It tells the crew about layered soils that can behave differently from top to bottom.
- It helps plan slopes, benching and shoring for deep excavations. See Deep Excavations and Protective Systems.
Limits of a report
- Borings are spot samples. Conditions between holes can differ.
- Ground conditions change with rain, thaw, vibration, nearby digging and time.
- The report does not replace OSHA's trench rules or the competent person's judgment.
Checklist
- Ask the general contractor or engineer for the geotechnical report before digging
- Review boring locations, groundwater and recommendations with the crew
- Compare what you see in the trench with the report; report surprises to the competent person
- Stop work and get an engineer if soil, water or ground behavior differ from expectations
- Keep the report with the site documents
Standards & references
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