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ZAPOSH CONSULTANCY AND SERVICES TO MAKE THE WORKPLACE SAFER, HEALTHIER AND MORE PRODUCTIVE

Focus on training • To know the hazards and recognize the importance of safety in excavation. • Make awareness to control the hazards and prevent accident / incident. • Factors that pose personnel working in excavation. • The role of a competent person prior and during excavation and trenching.

Definitions • 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 ft. • Shield - a structure able to withstand a cave-in and protect personnel. • Shoring - a structure that supports the sides of

an excavation and protects against cave-ins.

Definition • Sloping - a technique that employs a specific angle of incline on the side of the excavation. • Benching - a method of protecting personnel inside excavation by cutting the sides of the excavation in the arrangement of one or more horizontal levels.

OSH Rule 1413 Shoring and timbering: •Thewalls of every excavation over 1m (3ft.) shall be supported by adequate shoring and timbering to prevent collapse; • Shoring or timbering in excavation over 6.6m (20 ft.) shall be designed by structural engineer…

Excavation Hazards • Cave-ins are the greatest risk. • Asphyxiation due to lack of • oxygen • Inhalation of toxic materials. • Falls Accidental severing of underground utility lines that may cause death or

in ju ry .

Excavation Hazards • Water accumulation • Access / egress •Movingmachinerynear the edge of the excavation • Struck by falling objects

Protection of personnel to potential cave-in • Slope or bench the side of the excavation • Support the side of the excavation, or • Place a shield between the side of the excavation and the work area

These workers are inside the trench with no protective system and has no

means of access

Inspections • Competent person should inspect the excavation -on a daily basis -after a rainstorm and - as needed when other hazard increasing occurrence are noticed.

Competent person • He / she must have had a specific training in and be knowledgeable about - Soilclassification - The use of protective equipment - The requirements of the standard • Must be capable of identifying the hazard, and authorized to immediately eliminate hazards

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

Protective system -

Sloping / Benching Trench box Shoring/sheeting

Excavation less than 3 ft. in depth do not require protective system if examines and determine that there are no potential from cave-in by a competent person.

Design of protective system • The employer shall select and construct - slopes and configurations of sloping and benching system. - support system, shield system and other protective system

Factors involved in a Protective designing • Soil classification.tem • Depth of cut. • Water content of soil. • Changes due to weather and climate. • Other operations in the vicinity. • Location where to excavate.

Soil Type • Stable Rock - is a natural solid mineral that can be excavated with vertical sides and remain intact while exposed; • Type A Soils are cohesive soils with an unconfined compressive strength of 1.5 tons per square foot (tsf) or greater; • Examples of this type of soil are: Clays, clay, sandy clays, and clay loam. silty

• ASoil is type ‘A’ IF: N-T hesoilisfissured - The soil is subject to vibration - The soilhas been previously disturbed – Thematerial is subject to other factors that would require it to be classified as a less stable material. - Water is present

Soil Type • Type B Soils are cohesive soils with an unconfined compressive strength greater than 0.5 tsf but less than 1.5 tsf; • Examples: Granular cohesionless soils including; silt, silt loam, sandy loam, and some sandy clay loam • Previously disturbed soils except those which would otherwise be classified as Type ‘C’ soil

Soil Type • Type C Soils are cohesive soils with an unconfined compressive strength of 0.5 tsf or less. • Examples: Granular soils including gravel, sand, and loamy sand • Submerged soil, or soil from which water is freely seeping

Sloping/Benching Sloping in Type ‘A’ Soil

Excavation walls shall be cut to forty five degrees angle from the vertical or cut to the angle of repose.

Sloping in Type ‘B’ Soil

Sloping in Type ‘C’ Soil

Sloping/Benching Benching shall be done in a manner that will not collapse the side of the excavation. Maximum depth of cut shall be at least 4 ft.

Trench Box/Shield System “Astructure that is able to withstand the forces imposed on it by a cave-in and thereby protect employees.”

Trench Box/Shield System Trench boxes are generally used in open areas, but they may also be used in combination with sloping and benching. The box should extend at least 18 inches above the surrounding area if there is sloping toward the excavation.

Shoring • “A structure such as metal hydraulic, mechanical or timber shoring system that supports the sides of an excavation and which is designed to prevent cave-ins.”

Shoring • Provides a framework to work in • Use wales, cross braces and uprights

Hazardous atmosphere • In location where oxygen deficiency or gaseous condition are known or suspected, the atmospheres in the excavation shall be tested before employees enter the excavation •Exhaustventilation and other means shall be provided

Protection of personnel from fall, falling of debris, vehicle and equipment • Perimeter protection shall be provided to prevent personnel, vehicles and equipment from falling into excavation such as; - Construction safety sign’s - Barricades - Safety nets – Stop log

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

ignals

Protection of personnel from fall, falling of debris, vehicle and equipment

a

• Excavated materials shall be placed

distance not less than 1/3 one third of the depth of the excavation • Materials such as boulders or stumps that may slide or roll into the excavation shall be removed or made

safe.

Protection of personnel from fall, falling of debris, vehicle and equipment • Put devices sufficient to retained and prevent excavated materials from falling into excavation • No employee shall be permitted to work under a loads handled by equipment and or beneath on top of worker.

• Wear Personal Protective Equipment.

Protection of personnel from fall, falling of debris, vehicle and equipment • Tools or materials shall be kept a minimum of 3 ft. away from the edge • No vehicle or machinery shall be driven, operated or located near the edge of an excavation at least a distance of one third 1/3 of it’s depth.

Protection from water When water is present in an excavation it is extremely hazardous to enter, precautionary measures should be taken for excavation over 1m (3ft.) • Divert water by means of ditches, dikes or other means to prevent water from entering excavation • Pumping out of water thru proper equipment which should be monitored by competent person

Access / Egress • Walkways or bridges with standard guardrails shall be provided when people need to cross over in the excavation

Access / Egress •A stairway, ladder, or ramp must be present in excavation that are 3 or more feet deep and should not exceed 50 feet of lateral travel for • the employees.

urface of the

excaft. from the vati on

sadders should extend 3

Access / Egress • Excavation should be properly backfilled, compacted as soon as possible • When excavation exceeds 20 ft in depth, ramps, stairs or mechanicalhoist is required • Ramps should be 4 ft in width when used for personnel access only.

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Prior to Excavation • Prior to excavation, underground utility lines must be determined. • Permit should be obtain when necessary Note: If there is suspected underground utility 2 ft below or adjacent to excavation, it must be dig manually.

Summary • The greatest risk in excavation is a cave-in. • Employees can be protected through sloping, shielding, and shoring the edge excavation • Excavation should be inspected by a competent person

TH

FIRS T E

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TH BES WAY E T

SAF WAYIS

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