TRENCH SAFELY

• Trenches 5 feet deep or deeper require a protective system.

• Trenches 20 feet deep or deeper require that a registered professional engineer design the protective system.

• Keep heavy equipment and excavation spoils at least 2 feet from the edge of the trench.

• Provide stairways, ladders, ramps, or other safe means of access and egress in all trenches 4 feet or deeper, with spacing no more than 25 feet apart. Consider providing access and egress for shallower trenches as well.

PROTECTIVE SYSTEMS

• Sloping protects workers by cutting back the trench wall at an angle away from the excavation.

• Shoring protects workers by installing aluminum, hydraulic, or other types of supports to prevent soil movement.

• Shielding protects workers by using trench boxes or other supports to prevent soil cave-ins.

COMPETENT PERSON

• Competent person: OSHA standards require that a competent person inspect the trench daily and whenever conditions change.

• A competent person is defined as someone capable of identifying existing and predictable hazards in the surroundings or working conditions that are unsanitary, hazardous, or dangerous to employees, and who has authorization to take prompt corrective measures to eliminate them (29 CFR 1926.32(f)).

FOUR TYPES OF SOIL

• Stable rock: Natural solid material that remains intact.

• Type A: Cohesive soil not previously disturbed with an unconfined compressive strength ≥1.5 tsf.

• Type B: Cohesive soil with an unconfined compressive strength >0.5 tsf and <1.5 tsf, including angular gravel, silt, silt loam, sandy loam, and, in some cases, silty clay loam and sandy clay loam.

• Type C: Cohesive soil with an unconfined compressive strength <0.5 tsf, including granular soils such as gravel, sand, loamy sand, or soil from which water is freely seeping.

CONFIGURATIONS

Sloping and benching systems: Configurations must follow OSHA guidelines as shown in Figure B-1

RESOURCES AND REFERENCES

OSHA 29 CFR 1926.32(f)

https://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_ id=10618

OSHA Trenching and Excavating Webpage URL

https://www.osha.gov/SLTC/trenchingexcavation/index.html

American Pipeline Contractors Association Excavation and Trenching Best Practices http://www.americanpipeline.org/images/safetyzone/BestPractices/English/ ExcavAndTrenching_Operators.pdf