Safe Excavation Access and Egress

 Excavation

 

Safe Excavation Access and Egress

OHSA Definition “An excavation is any man-made cut, cavity, trench, or depression in the Earth's surface formed by earth removal.” A trench is considered an excavation. Employees working on or near construction sites must be protected from cave-in when the excavation is 4 ft or more in-depth.

If excavations are made entirely of stable rock, then Cave-In protection is not required or If no potential cave-in is found after examination by a competent person In less than 4 ft in depth.

There are numerous hazards associated with excavation and including the weight of nearby vehicles, equipment, vibration, underground utilities, water, and soil erosion. All the factors must be taken by the competent person into consideration when evaluating an excavation. (it should be kept in mind that the hazards and/or conditions can change frequently and should be continuously re-evaluated.

The materials removed from the excavation (spoils pile) and surcharge loads (the equipment kept too close to the vertical walls of the trench) increase the likelihood of collapse. Additionally, equipment vibration, adverse weather conditions, and groundwater can change the condition and classification of soils.

A competent person is someone who can identify the existing or predictable hazards in excavations, who has authority to take corrective actions as necessary, who is familiar with the OSHA regulations and standards for excavations, who is knowledgeable in soil analysis and classification, as well as the erection, use, and precautions for the protective system on site.

*RPE is a person registered as an engineer (Registered Professional Engineer) in the state where the excavation is being performed.

The safe trenching work procedures the following:

• (Identification of competent person.

• Check and verify ground utility locations, any adjacent structures or surface load, and the water table.

• Determine the soil classification through testing.

• Verify protective system installation and setup.

• Provide safe access.

• Comply specified in the “Excavation, Trenching, and Shoring” regulations.

• Conduct site inspections prior to the start of work, after any weather event and as needed.

Soil Classifications

It is crucial to correctly classify soil types before selecting and using a protective

system. Soil types are classified as Type A, B, or C. In order to classify soil, one visual test and manual test are required. If soil is classified as Type C, then no testing is required.

Protective Systems

The Protective systems include but are not least sloping and benching, shoring, and shield systems. Protective systems are required under the following conditions:

• Under 4 ft deep when there is a potential for cave-ins.

• Four to 20 ft deep.

• Sloping or benching.

• Shield or shoring systems.

• Over 20 ft deep—RPE must design the protective system, or it should be approved by the manufacturer’s tabulated data.

Sloping

The process of removing soil to eliminate the chance of cave-in is called sloping. The soil classification determines the required maximum allowable slope.

Shoring

Shoring is the most commonly used method of worker protection in excavations. It is lightweight and easy to install.

Shields (Trench Boxes)

Trench Boxes/Shields are provided to protect workers working in the confines of the shields.

Additionally, the shield must be designed and be in good condition and should be used properly.

The excavation should not be deeper than 2 ft from the bottom of the shield of the shields don't go all the way to the bottom of the trench. The shield system should be designed in a way to resist the calculated forces created by the trench wall for the full depth of the open trench.

RPE-Designed Protective Systems

The protective system for use on a specific project can be designed by an RPE, by considering the type of soil and other concerns that exist/may exist at the excavation site. Daily inspection has to be performed by a competent person to verify the site conditions and any changes that need to take place.

Safe Entry and Exit

Any trench that is 4 ft or more in-depth should have a safe means of entry and egress for all workers to get in and out of the trench. It is required to be within 25 ft of lateral travel. The most common method for access is a straight ladder or an extension ladder. The ladder used in the trench must be extended 3 ft above the landing platform (step ladder is not permitted), stairway, ramp, or other means of entry and egress, excavator buckets, backhoes, and other plant & equipment are not allowed to be used as a means of egress.

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