Excavation Safety

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EXCAVATION SAFETY

1. Excavation Hazards

2. Focus of Training

3. Protection of Employees

4. Requirements for Protective Systems

5. Factors Involved in Designing a Protective System

6. Hazardous Conditions

7. Protection from fall, Falling Loads, and Mobile Equipment

8. Competent Person

9. Closing

INJURY AND DEATH

• Excavating is one of the most

hazardous construction operations

• Most accidents occur in trenches

5‐15feet deep

• There is usually no warning before

a cave‐in

Excavation Cave‐ins are greatest risk

EXCAVATION HAZARDS

Cave the Other hazards include:

• Asphyxiation due to lack of oxygen

• Inhalation of toxic materials

• Fire

• Moving machinery near the edge of the

excavation can cause a collapse

• Accidental breaking of underground

utility lines

Excavation – a man‐made cut, , cavity, trench, or depression

formed by earth removal

Trench – a narrow excavation. The depth is greater than the

width, but not wider than 4 meters

Shield ‐ a structure able to withstand a cave‐in and protect

employees

Shoring ‐ a structure that supports the sides of an

excavation and protects against cave‐ins

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

• The risk of working in excavation

• How to protect employees from cave‐ins

• Factors that pose a hazard to employees working in

excavations

• The role of a competent person in excavation site

PROTECTION OF EMPLOYEES

• Employees should be protected from

cave‐ins by using an adequately designed

protective system

• Protective systems must be able to resist all

expected loads to the system

A well designed system

REQUIREMENTS FOR PROTECTIVE SYSTEMS

wellprotective • Correct design of sloping and benching systems

• Correct design of support systems, shield systems, and

other protective systems

Plus

Appropriate handling of materials and equipment

Plus

Attention to correct installation and removal

Equals Protection at EXCAVATION SAFETY

DESIGN OF PROTECTIVE SYSTEMS

The employer shall select and construct:

• slopes and configurations of sloping and benching systems

• 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

EXPOSED TO POTENTIAL CAVEINS

• Slope or bench the sides of the  xcavation,

• Support the sides of the excavation, or

• Place a shield between the side of the excavation and the work area

CAVE IN HAZARD

This excavation has inadequate support posts and egress & access

INADEQUATE PROTECTIVE

SYSTEM

INADEQUATE PROTECTIVE SYSTEM

This worker is in a trench with no protective system, that is not sloped or benched and has no means of egress

FACTORS INVOLVED IN DESIGNING A

PROTECTIVE SYSTEM

• Soil classification

• Depth of cut

• Water content of soil

• Changes due to weather and climate

• Other operations in the vicinity

SHORING

General

• Provides a framework to work in

• Uses wales, cross braces and uprights

• Supports excavation walls

• Must know soil type

• Must know depth and width of excavation

SLOPING & BENCHING

The design of protection systems, including sloping, benching, shoring and shielding,  will depend primarily on two factors:

• The types of soil encountered, and in the depth of the excavations

• Persons working in excavations can be protected by sloping and benching the sides of the excavation in accordance with the industrial safety and Health Law

SLOPING & BENCHING

Type Slope maximum

degree

Soil Wet soil 1 : 1 ~ 1 : 1.5 45° ~ 34°

Dry soil 1 : 0.5 ~ 1 : 1 63° ~ 45°

Rock Weathered

rock

1 : 0.8 51°

Loose rock 1 : 0.5 63°

Stable rock 1 : 0.3 73°

TRENCH SHIELD

A trench shield was built around this work

area

HYDRAULIC TRENCH SUPPORT

• Using hydraulic jacks the

operator can easily drop the

system into the hole

• Once in place, hydraulic pressure is increased to keep the forms in place

• Trench pins are installed in case of hydraulic failure

MATERIALS AND EQUIPMENT

Equipment used for protective systems must not have damage or defects that

impair function.

If equipment is damaged,

the competent person must examine it to see if it is suitable for continued use.

If not suitable, remove it from service until a professional engineer approves it for use.

PROTECTION FROM VEHICLES

• Install barricades

• Hand/mechanical signals

• Stop logs

• Grade soil away from

excavation

• Fence or barricade

trenches left overnight

HAZARDOUS CONDITIONS

The weight and vibrations of the crane make this a very hazardous condition. They should not be working under this crane.

• Don’t place spoil soil within 1

SPOILS

meter from edge of excavation

• Rocks, stones or other debris

will not be left any closer than 2 meters to the edge of the excavation

• Measure from nearest part of the spoil to the excavation edge

• Place spoils so rainwater runs away from the excavation

• Place spoil well away from the excavation

OTHER EXCAVATION HAZARDS

• Water accumulation

• Oxygen deficiency

• Toxic fumes

• Access/Egress

• Falls

• Mobile equipment

WATER IS HAZARDOUS

When water is present in an excavation, it is

extremely hazardous to enter

Note that these workers are not wearing hardhats to protect them from materials falling into the trench

WATER = CAVEIN HAZARD

These workers must be protected from cave‐in. Note the water in the bottom of the trench. This is a very hazardous condition!

HAZARDOUS ATMOSPHERE

Test excavations before an employee enters the excavation for:

• Oxygen deficiency

• High combustible gas

concentration

• High levels of other

hazardous substances

This ladder does not meet the

i t f th t d d

MEANS OF EGRESS

A stairway, ladder, or ramp must  requirements of the standard be present

in excavations that are 4 or more feet deep,

and within 25 feet of the employees

The ladder should extend 3 feet

above the excavation

These ladders

ACCESS AND EGRESS

two which are latched together are not an adequate means of egress The ladder  should extend 3 feet above the top of the

excavation Hanging electrical cables touching the aluminum ladder

PROTECTION FROM FALLS, FALLING

LOADS, AND MOBILEEQUIPMENT

• Install barricades

• Use hand/mechanical signals

• Grade soil away from excavation

• Fence or barricade trenches left overnight

• Use a flag man when signs, signals and barricades are not enough protection

• All heavy equipments (e.g. compressor units, generators, etc.) shall be kept minimum of 2 meters away from the edge

• Wheel locks are to be placed on any wheeled vehicle, which is parked, in close proximity to an excavation.

• Heavy vehicular traffic shall not be permitted near un‐shored sides

• Location of underground utilities

COMPETENT PERSON

Must have had specific training in and

be knowledgeable about:

• Soils classification

• The use of protective systems

• The requirements of the

Standard 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:

• Before work starts and as

needed,

• After rainstorms, high winds

or other occurrence which may

increase hazards, and

• When you can reasonably

anticipate an employee will be

exposed to hazards.

INSPECTIONS 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:

• Evaluate soil conditions

• Construct protective systems

• Test for low oxygen, hazardous

fumes and toxic gases

• Provide safe in and out access

• Contact utilities

• Determine the safety Fissure

equipment needed

SUMMARY

• The greatest risk in an excavation is a cave‐in.

• Employees can be protected through sloping,

shielding, and shoring the excavation.

• A competent person is responsible to inspect the

excavation.

• Other excavation hazards include water

accumulation, oxygen deficiency, toxic fumes, falls,

and mobile equipment.

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