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Construction Depot

Safety and health newsletter for the Oregon construction industry

September 20, 2016

 

Excavation safety: requirements for competent persons

If you work in an excavation that is at least five feet deep, you must be protected from a cave-in. Additionally, when a competent person determines that there's a potential for an excavation to cave in, you must be protected, regardless of its depth. A designated competent person who has training in soil analysis, protective systems, and Oregon OSHA's Division 3, Subdivision P, Excavation rules must be on site to classify the soil, select a protective system, oversee installation, and inspect the system after installation.

A competent person must have authority to immediately correct hazards and to order employees to leave the excavation until the hazards have been corrected. An employee who is trained and can identify excavation hazards but doesn't have the authority to correct them is not a competent person. A competent person's responsibilities can be shared by other designated employees at the excavation site, as long as they know their respective roles in keeping the excavation safe.

If there are no existing hazards, a competent person can leave the excavation site for a short time, but must be present when a protective system is moved, when soil conditions change, or when new hazards arise that require the competent person's judgment.

Oregon OSHA's Division 3, Subdivision P, Excavation rules have the following requirements for competent persons:

Access and egress

Structural ramps that are used only by employees as a means of access or egress from excavations must be designed by a competent person. Structural ramps used for equipment must be designed by a competent person qualified in structural design.

Water accumulation

When equipment is used to control or prevent water from accumulating in an excavation, the equipment and the operation must be monitored by a competent person.

Inspections

A competent person must inspect the excavation, adjacent areas, and protective systems for evidence of a possible cave-in, hazardous atmospheres, or other hazardous conditions before the work starts, after every rainstorm, and as needed throughout the shift. Inspections are necessary only when employees are exposed. When the competent person finds evidence that employees may be in danger, they must leave the excavation until the necessary precautions have been taken to ensure their safety.

Protective systems

Protective systems are required in excavations unless they are less than five feet deep, cut in solid rock, or a competent person determines there is no potential for a cave-in.

When a protective system is damaged, a competent person must evaluate its suitability for continued use. Damaged systems that are unable to support intended loads must be removed from service and must be evaluated and approved by a registered professional engineer before being returned to service.

Soil classification

A competent person must conduct visual and manual soil tests before anyone enters an excavation and classify the soil as Stable Rock, Type A, Type B, or Type C. Visual testing involves looking at the soil and the area around the excavation site for signs of instability. Manual testing involves evaluating a sample of soil from the excavation to determine qualities such as cohesiveness, granularity, and unconfined compressive strength. Soil can be tested either on site or off site, but should be tested as soon as possible to preserve its natural moisture.

If conditions affecting its classification change in any way, the competent person must reclassify the soil to reflect the changed circumstances.

Sloping and benching

When there is a surcharge load – a load on ground adjacent to sloped or benched excavation – a competent person must determine how much the slope must be reduced below the maximum allowable slope and ensure that the change is made before excavation work continues.

 

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