excavation safety1

7/28/2019 Excavation Safety1

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Excavation Safety


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Objectives:

Highlight the hazards of working in a excavation.

How to protect employees from cave-ins.

Factors that pose a hazard to employees working inexcavations.

The role of a competent person at an excavation site.


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Introduction:

Cave-ins are perhaps the most feared trenching hazard.

But other potentially fatal hazards exist including:

Asphyxiation due to lack of oxygen in a confined space

Inhalation of toxic fumes, drowning, etc.

Electrocution or explosions can occur when workerscontact underground utilities.


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Definitions:

Cave-In:

Means the separation of a mass of soil or rock material from the side of an

excavation, or the loss of soil from under a trench shield or support system, and itssudden movement into the excavation,either by falling or sliding, in sufficientquantity so that it could entrap, bury, or otherwise injure or immobilize a person.


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Definitions:

Excavation Falling onto the Personnel:

A RELATIVELY SMALL COLLAPSE MIGHTINVOLVE A CUBIC METRE OF SOIL, BUT

A CUBIC METRE OF SOIL WEIGHS OVER A TONNE.

PERSONNEL BURIED AT THE BOTTOMOF THE TRENCH UNDER THIS VOLUME

OF MATERIAL WOULD BE UNABLE TOBREATHE DUE TO THE PRESSURE ONTHEIR CHESTS, AND SO WOULDQUICKLY SUFFOCATE AND DIE.


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Anatomy of a Cave - In:

There is usually no warning before a cave-in


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Definitions Continued:

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 15 feet.

Shield - a structure able to withstand a cave-in andprotect employees

Shoring - a structure that supports the sides of anexcavation and protects against cave-ins

Sloping - a technique that employs a specific angle of incline on the sides of the excavation. The angle variesbased on assessment of impacting site factors.


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Excavation Hazards:

Surface encumbrancesUtilities Access/Egress

Vehicle trafficFalling loadsMobile equipmentHazardous atmospheres

Water accumulation Adjacent structuresLoose rock or soilFallsCave-in


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General Requirements:

Before any excavation actually begins, the employer must determine the estimated locationof utility installations: Sewer, telephone, fuel, electric, water lines, or any other under groundinstallations that may be encountered during digging.

A competent person will inspect, on a daily basis, excavations and adjacent areas for possible cave-ins, failure of protective systems and equipment, hazardous atmospheres, or other hazardous conditions.

Takes prompt corrective measures to eliminate hazards.

Adequate protective systems will be utilized to protect employees. This can be accomplishedthrough: Sloping, Shoring, or Shielding.

Workers must be supplied with and wear any PPE deemed necessary to assure their protection.

Mechanical excavators and power tools should not be used within 0.5 m

If a trench is 4 feet or deeper, stairways, ramps, or ladders will be used.

The employees must not have to travel any more than 25 feet to reach the stairways, ramps,or ladders.

4 feet and more trenches Toxic and hazardous atmosphere will be tested daily.


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Access:

The ladder should extend 3feet above the excavation


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Access:

These twoladders which

are lashed

together are notan adequatemeans of egress

The ladder should extend 3rungs above the

top of theexcavation


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Ladder to be 1 Meter Above Wall:


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Excavation Protection Systems:

There are three basic protective systems used in excavations andtrenches:

1. Sloping and Benching Systems

2. Shoring Systems

3. Shielding Systems


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Simple Sloping:


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Benching:


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Shoring Systems:

Support system for trench faces used toprevent movement of

soil, undergroundutilities, foundations.

There are two basictypes of shoring,timber and aluminumhydraulic.


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Shoring Systems:


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Timber Shoring Installations:


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Hydraulic Shoring:


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Pneumatic Shoring:


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Shielding Systems:

A- Trench Boxes:

The space between theoutside of the trenchbox and the face of thetrench should be smallas possible, andbackfilled to preventlateral movement of thebox.


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Excavation Inspections:

Daily Inspections of ALL excavations by Competent Personat Start of shift, or as needed, following rainstorms or other hazard-increasing event:

Possible cave-insProtective system failureWater accumulationHazardous atmospheres

Competent person has authority to remove workers

from


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Causes of Cave Ins:


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Causes of Cave Ins:

When water is presentin an excavation it isextremely hazardous to

enter. Also no headprotection


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Causes of Cave Ins:

Note: telephone poleadjacent to excavation,not supported /

removed


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Inadequate Protective System:

This excavation hasinadequate supportposts and egress

access.


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Inadequate Protective System:

This worker is in atrench with noprotective system, that

is not sloped or benched and has nomeans of egress.


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Hazardous Condition:

The weight andvibrations of themachinery above make

this a very hazardouscondition.

They should not beworking under anymachinery.


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Hydraulic Trench Support:

Using hydraulic jacks theoperator can easily dropthe system into the hole.

Once in place, hydraulicpressure is increased tokeep the forms in place.

Trench pins are installedin case of hydraulic failure.


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Hazardous Atmosphere:

Test excavations more than 4feet before an employeeenters the excavation for:

Oxygen deficiency.

High combustible gas

concentration.

High levels of other hazardous substances.


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Means of Egress:

A stairway, ladder, or ramp must be presentin excavations that are

4 or more feet deep,and within 25 feet of the employees.

The ladder shouldextend 3 feet above theexcavation


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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 theexcavation.

Other excavation hazards include water accumulation,oxygen deficiency, toxic fumes, falls, and mobileequipment.


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REMEMBER:

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