Excavations (OSHA)

Excavation Hazards?

1. Cave-ins are the greatest risk 2. Asphyxiation due to lack of oxygen 3. Inhalation of toxic materials 4. Fire 5. Moving machinery near the edge of the excavation can cause a collapse 6. Accidental severing of underground utility lines

Injury and Death

1. Excavating is one of the most hazardous construction operations 2. Most accidents occur in trenches 5-15 feet deep 3. There is usually no warning before a cave-in

Excavation (Def)

Excavation – a man-made cut, cavity, trench, or depression formed by earth removal.

Trench (Def)

Trench – a narrow excavation. The depth is greater than the width, but not wider than 15 feet.

Shield (Def)

Shield – a structure able to withstand a cave-in and protect employees

Shorting (Def)

Shoring – a structure that supports the sides of an excavation and protects against cave-ins

Sloping (Def)

Sloping – a technique that employs a specific angle of incline on the sides of the excavation. The angle varies based on assessment of impacting site factors.

Focus of Training

1. The greatest risk at an excavation 2. How to protect employees from cave-ins 3. Factors that pose a hazard to employees working in excavations 4. The role of a competent person at an excavation site

The employer shall select and construct :

1. slopes and configurations of sloping and benching systems 2. support systems, shield systems, and other protective systems Shield – can be permanent or portable. Also known as trench box or trench shield. Shoring – such as metal hydraulic, mechanical or timber shoring system that supports the sides Sloping – form sides of an excavation that are inclined away from the excavation

Protect Employees Exposed to Potential Cave-ins

1. Slope or bench the sides of the excavation, 2. Support the sides of the excavation, or 3. Place a shield between the side of the excavation and the work area

Factors Involved in Designing a Protective System

1. Soil classification 2. Depth of cut 3. Water content of soil 4. Changes due to weather and climate 5. Other operations in the vicinity

Shoring

General 1. Provides a framework to work in 2. Uses wales, cross braces and uprights 3. Supports excavation walls OSHA tables provide shoring data 1. Must know soil type 2. Must know depth and width of excavation 3. Must be familiar with the OSHA Tables

Hydraulic Trench Support

1. Using hydraulic jacks the operator can easily drop the system into the hole 2. Once in place, hydraulic pressure is increased to keep the forms in place 3. Trench pins are installed in case of hydraulic failure

Materials and Equipment

1. Equipment used for protective systems must not have damage or defects that impair function. 2. If equipment is damaged, the competent person must examine it to see if it is suitable for continued use. 3. If not suitable, remove it from service until a professional engineer approves it for use.

Protection from Vehicles

1. Install barricades 2. Hand/mechanical signals 3. Stop logs 4. Grade soil away from excavation 5. Fence or barricade trenches left overnight

Spoils

1. Don’t place spoils within 2 feet from edge of excavation 2. Measure from nearest part of the spoil to the excavation edge 3. Place spoils so rainwater runs away from the excavation Place spoil well away from the excavation

Other Excavation Hazards

1. Water accumulation 2. Oxygen deficiency 3. Toxic fumes 4. Access/Egress 5. Falls 6. Mobile equipment

Hazardous Atmosphere

Test excavations more than 4 feet before an employee enters the excavation for: 1. Oxygen deficiency 2. High combustible gas concentration 3. High levels of other hazardous substances

Means of Egress

A stairway, ladder, or ramp must be present in excavations that are 4 or more feet deep, and within 25 feet of the employees

Access and Egress

The ladder should extend 3 feet above the top of the excavation

Protection from Falls, Falling Loads, and Mobile Equipment

1. Install barricades 2. Use hand / mechanical signals 3. Grade soil away from excavation 4. Fence or barricade trenches left overnight 5. Use a flagger when signs, signals and barricades are not enough protection

Competent Person

Must have had specific training in and be knowledgeable about: 1. Soils classification 2. The use of protective systems 3. The requirements of the standard 4. Must be capable of identifying hazards, and authorized to immediately eliminate hazards

Inspections of Excavations

A competent person must make daily inspections of excavations, areas around them and protective systems: 1. Before work starts and as needed, 2. After rainstorms, high winds or other occurrence which may increase hazards, and 3. When you can reasonably anticipate an employee will be exposed to hazards.

Inspection of Excavations

If the competent person finds evidence of a possible cave-in, indications of failure of protective systems, hazardous atmospheres, or other hazardous conditions: Exposed employees must be removed from the hazardous area Employees may not return until the necessary precautions have been taken

Site Evaluation Planning

Before beginning excavation: 1. Evaluate soil conditions 2. Construct protective systems 3. Test for low oxygen, hazardous fumes and toxic gases 4. Provide safe in and out access 5. Contact utilities 6. Determine the safety equipment needed

Summary

1. The greatest risk in an excavation is a cave-in. 2. Employees can be protected through sloping, shielding, and shoring the excavation. 3. A competent person is responsible to inspect the excavation. 4. Other excavation hazards include water accumulation, oxygen deficiency, toxic fumes, falls, and mobile equipment.