EXCAVATION WORK GUIDELINES

7/29/2019 EXCAVATION WORK GUIDELINES

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OHS System - Corporate

S2 OHS 17Excavation Work

GuidelinesPage 1 of 9

EXCAVATION WORK GUIDELINES

1.0 PURPOSE

1.1 The Shoalhaven City Council is regularly involved in excavation work.Infrastructure such as stormwater drainage, water supply and waste waterdisposal all require excavation work. This work is undertaken at various sites (across roads, in footpath areas, through private property), in various soil types(i.e. sandstone, shale, clay, sand, silt) under wet and dry conditions and atvarious depths.

2.0 SCOPE

2.1 The objective of these guidelines is to assist employees to properly plan anyexcavation work, thus ensuring a safe system of work and appropriate controlmeasures are implemented to prevent persons being injured. Section 5.0 ofthis guideline has been prepared by extracting relevant information from theCode of Practice for Excavation.

2.2 The system of work and control measures selected is generally determined byindividual job factors identified in the consultation and risk assessmentprocess. There are three crucial times to perform a risk assessment:2.2.1 At the design and planning stage this is the best time to eliminate

hazards, and is usually done by an engineer.2.2.2 Prior to works commencing to make sure that all planning assumptionsare valid, and all employees and resources are fit for purpose. This isusually performed by the supervisor of the crew.

2.2.3 During the works, to make sure that systems are working properly andthat the initial hazards and risks identified as part of the riskassessment process have not changed

3.0 REFERENCES AND ASSOCIATED DOCUMENTS

3.1 OHSOHS Act 2000

3.2 OHSOHS Regulation 2001.3.3 Code of Practice Excavation Work 31 March 2000.3.4 Guide for Front End Loader and Excavator drivers a WorkCover NSW

publication.3.5 SCC OHSOHS Risk Register.3.6 SCC OHSOHS Authorities, Responsibilities & Accountabilities for Managers,

Supervisors and Employees Policy.3.7 SCC Confined Space Procedure3.8 SCC Working at Heights

Unique Document

Number: S2 OHS 17

Document Name:Excavation Work

Guidelines

Responsible Group: Assistant General

Manager

Reference: 6841e

PRD10/171

Adopted: 12.04.1996 Last Amended: 06/07/2010 Review Date: 06/07/2013 Version: 6 Page 1 of 9


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4.0 DEFINITIONS

Some of the terms used in these guidelines are:

Angle of repose The angle to the horizontal at which the material in the cutface is stable and does not fall away. Note: Differentmaterials have different angles of repose, for example solidrock 90 degrees and sand 30 degrees.

Barrier Anything that blocks a way or makes a separation i.e. shadecloth, sheet ply, plastic mesh webbing, etc. Note: Barriers arenot necessarily designed to prevent falls. Single strand plastictapes should not be used as a barrier.

Barricade An object such as jersey kerb truck or plant capable of

providing effective protection against traffic entering the worksite.

Batter or Slope An angle in relation to the horizontal surface.

Benching The horizontal stepping of the face, sides, walls or bottom ofan excavation.

Competent person Means a person who has acquired through training,qualification, or experience, or a combination of these, theknowledge and skills enabling that person to perform thespecified tasks.

Construction

work- includes

Building including excavation, and the construction,

alteration, renovation, repair, maintenance and demolition ofall types of buildings or structures. Civil engineering, includingexcavation, and the construction, structural alteration, repair,maintenance and demolition of, for example, airports, docks,harbours, inland waterways, dams, river and avalanche andsea defence works, roads and highways, railways, bridges,tunnels, viaducts and works related to the provisions ofservices such as communications, drainage, sewerage, waterand energy supplies. The erection and dismantling ofprefabricated buildings and structures as well asmanufacturing of prefabricated elements on the construction

site.Cover A steel plate or other suitable material capable of

withstanding the loads that may be imposed upon it and ofsufficient weight or secured to prevent removal by children.

Cutting An open cut excavation having a single wall or face.

Excavation work Work involved in the excavation or filling of trenches, ditches,shafts, drifts, rises, tunnels, pier holes, cuttings, benches,wells or canals or any similar work.

Face An exposed sloping or vertical surface resulting from theexcavation of material.

Unique Document

Number: S2 OHS 17


Guidelines


Manager

Reference: 6841e

PRD10/171



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Fence Continuous enclosure not less than 1800mm in height thatprevents unauthorised access to the work place and of such

strength to remain erect in position during all conditions.GeotechnicalEngineer

An engineer whose qualifications are acceptable formembership of the Institution of Engineers, Australia and whohas qualifications and experience in soil stability andmechanics and excavation work.

Handrail A rail one meter in height (plus or minus 100mm) effectivelysupported, secured and of such rigidity and strength capableof providing support so as to prevent persons falling.

Open Excavation An excavation where the width is equal to or greater than thedepth.

Plant Includes any machinery, equipment (including scaffolding),appliance, implement or tool and any components or fittingsor accessories to them.

Shoring The use of timber, steel or other structural material for thepurpose of providing effective and adequate temporarysupport to maintain the stability of the walls of an excavation.

Support structure A shoring system to maintain the stability of the walls and roofof an excavation and includes a trench shield.

TrenchAn excavation having a depth that exceeds its width,measured at the bottom.

Trench shield A structure with two vertical side plates permanently braced

apart by cross frames or struts designed to resist thepressure from the walls of a trench and capable of beingmoved as a unit. The trench shield is intended to provide asafe working place for persons while work in an excavation isbeing carried out.

Waling A horizontal beam supporting vertical timbers, runners orsheeting.

Work methodstatement

A statement that outlines the manner of carrying out the workin a safe and healthy way.

Zone of influence The volume of soil around the excavation affected by anyexternal load, eg vehicles, plant, excavated material.This volume is generally assumed to be that formed by planesextending from the load to a maximum angle to the horizontalof 30 degrees (1V:1.75H) in the case of sand and 45 degrees(1H: 1V) for clay.

5.0 DESCRIPTION

5.1 Responsibilities

Unique Document

Number: S2 OHS 17


Guidelines


Manager

Reference: 6841e

PRD10/171



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5.1.1 The OHS Regulation 2001 identifies a number of provisions in relation

to Excavation Work.

5.2.2 According to the Regulation (Chapter 8 Part 8.5) an employer mustensure that:a) The excavation is stable; No excavation work that is likely to reduce

the stability of any part of a building or structure is commenced;b) Adequate measures are taken in the immediate vicinity of excavation

work so as to prevent the fall of mobile plant or materials into theexcavation;

c) No materials are placed, stacked or moved near the edge ofexcavation work so as to endanger a person present below;

d) An adequate system of safety is in place to control risks to health andsafety arising from unplanned contact with electricity cables, gasmains and other utility services;

e) Excavation work at a depth of 1 metre or more is inspected by acompetent person at the intervals determined during the riskassessment for the work;

f) There is a safe means of access to and egress from excavations.

5.3 The responsibilities of the following positions within Council include (but are

not limited to):

5.3.1 Employees before working in or around an excavation be aware ofthe risks and the control measures adopted on each site. Continuallyreassess the conditions of the excavation and bring any changes to theattention of their supervisors. Ensure that the appropriate PPE(including hard hats) are worn.

5.3.2 Supervisors ensure employees on the excavation sites are properlyinducted onto the site, aware of the hazards; understand the system ofwork and able to provide input to the operation. Continually reassessthe conditions of the excavation and take action as appropriate. Provideemployees with appropriate PPE (including hard hats).

5.3.3 Managers are to provide the necessary support for supervisors,ensure that these guidelines are available and understood, and ensurethat at the design phase hazards are eliminated from excavationswhere possible.

5.4 Hazards:

5.4.1 The following hazards are commonly associated with excavation workand should be considered during the risk assessment process;a) The fall or dislodgement of earth and rockb) The instability of the excavation or any adjoining structure

c) The inrush or seepage of waterUnique Document

Number: S2 OHS 17


Guidelines


Manager

Reference: 6841e

PRD10/171



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d) Unplanned contact with utility services eg, electricity cables and gasmain (control measure, ensure the location of underground, above

ground and overhead services are identified and clearly marked)e) The placement of excavated materialf) Falls into excavationsg) The movement and positioning of heavy plant and equipment

affecting the excavationh) Ground vibration affecting the stability of the excavationi) Vehicle movementj) Excessive noise from the operation of machinery and plantk) Manual handling injuriesl) Changes to excavation conditions

5.5 Benching and Battering Excavation Walls(As per the Code of Practice Excavation March 2000)

5.5.1 Both benching and battering of excavation walls are methods of workwhich minimise the risk of the soil or rock slipping onto the excavation.

5.5.2 Benching is the creation of stepped sides to an excavation.This is done by forming a series of vertical and horizontalplanes forming a number of steps in the wall of an excavation.(See Figure 3a.) Benching is used to reduce the height of thevertical wall of an excavation by cutting a series of steps. A riskassessment should be conducted to determine the height and

width of the steps necessary to ensure stability.5.5.3 A batter is where the wall of an excavation is sloped back to a

predetermined angle. Battering should commence from thebottom of the excavation. (See Figure 3b.)When benching or battering the walls of an excavation, anangle of repose of 45 degrees should not be exceeded unlesscertified in writing by a geotechnical engineer.

Unique Document

Number: S2 OHS 17


Guidelines


Manager

Reference: 6841e

PRD10/171



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Figures taken from Code of Practice Excavation Work

Page 15 & 16,Section 3. Work Systems and Control Measures

Note: When determining the depth of an excavation or trench it is important toaccount for any over excavation that may be required. For examplemost engineering drawings that relate to stormwater pipelines specify

depth from an approximation of the natural surface to the pipe invert.The trench will need to be this deep plus the thickness of pipe and thethickness of the bedding sand.

5.6 Materials and Loads Beside and Near Excavations

5.6.1 It is a legal requirement that employers must ensure that materials arenot placed or stacked near the edge of any excavation work so as toendanger persons employed below.

Unique Document

Number: S2 OHS 17


Guidelines


Manager

Reference: 6841e

PRD10/171


1.5m min

45o max

45o min

1m min

1m min1m min

1.5m max

1.5m max

1.5m min1.5m min


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5.6.2 It is a further requirement that no load be placed or moved near theedge of any excavation work where it is likely to cause a collapse of the

side of the excavation work and thereby endanger any person.5.6.3 To reduce the risk of excavation collapse, excavated or other loose

material should be effectively stored or retained away from theexcavation.

5.6.4 Excavated material should be placed outside the zone of influence.5.6.5 Alternatively the support system should be designed to accommodate

such additional loads including ground water pressures, saturated soilconditions and saturated materials.

5.6.6 Mechanical plant, vehicles, storage of materials or any heavy loadsshould be prevented from approaching within or encroaching on thezone of influence of an excavation unless the support system has been

specifically designed for such loads. (See Figure 5 a,b,c,&d.)5.6.7 Where the risk assessment has identified a risk of collapse as a result

of loads or materials beside or near the excavation, shoring must be inplace before any person enters the excavation. The following measuresshould also be considered before starting excavation work:a) Controlling access to exclude persons from hazardous areas, eg

relocating means of access;b) Moving and storing loads outside the zone of influence of the

excavation;c) Adopting a system of dig and lay to reduce the risk of overloading

from pipes stores near the excavation;d) Provision of wheel stoppers to limit movement of mobile equipment

adjacent to the excavation;e) Reducing the number of trench shields stored near excavation by

pulling along trench shields or drag box and backfilling as theexcavation progresses securing all loose materials in place, includingstored pipes.

5.6.8 When working on a slope, a risk assessment should be conducted todetermine the safest side of the excavation to dump soil and excavatedmaterial. This would often be on the lower side of the slope to reducethe risk of wall collapse or material falling into the excavation. Site

factors would have to be considered (See Figure 5d). There are alsorisks in backfilling on sloping sites. For more information about workingon sloping sites see the WorkCover NSW Publication A Guide for frontend loader and excavator drivers.

5.75.7.1 Emergency and Rescue Procedures in the event of an accident, injury

or other emergency, including the means of rescuing persons, andarrangements where necessary to protect any other persons in thevicinity. Risk factors such as the nature of possible emergencies, sizeand location of the work place, number of staff on site and the location

the nearest emergency services.Unique Document

Number: S2 OHS 17


Guidelines


Manager

Reference: 6841e

PRD10/171



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5.7.2 Control measures for emergency procedures may include;a) Development and communication of a warning system and safe and

rapid evacuation procedures including injured persons.b) Having trained personnel to oversee evacuation and rescue

procedures until emergency services arrive.d) Appropriate medical treatment of injured personnel until emergency

services arrive.e) Shutting down of work and machineryf) Provision of fire fighting and rescue equipmentg) Display of evacuation procedures in appropriate work site locations.

Figures taken from Code of Practice Excavation WorkPage 23, Section 3. Work Systems and Control Measures

Note: For some site locations it may be appropriate for a backhoe to encroach withinthe zone of influence and place a front bucket of sand in a trench. This load isgenerally around two tonnes and the operation is performed with employeesaway from the position of sand placement. The operation and excavation wallmust be constantly monitored by the site supervisor.In some instances a painted line at the edge of the zone of influence may bemore appropriate than a timber wheel stopper.

Unique Document

Number: S2 OHS 17


Guidelines


Manager

Reference: 6841e

PRD10/171



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In either case discussions between the operator and the site supervisor needto be recorded in the form of a Risk Assessment.

5.7 Shoring

5.7.1 In circumstances where shoring is required and where there isinadequate space for benching or battering employees are required torefer to the Code of Practice for Excavation.

6.0 QUALITY CONTROL

6.1 Implementation of this procedure shall be audited through workplaceinspections and desktop audits.

7.0 APPENDICIES

7.1 NIL

8.0 RESPONSIBILITIES FOR IMPLENTATION

8.1 The Human Resources Manager is allocated overall responsibility for theimplementation of this procedure and all documents prepared for inclusioninto the OHS&R Management System.

9.0 PROCEDURE OWNER

9.1 The OHS Unit (OHS Co-ordinator) is assigned ownership to ensure theprocedure is maintained and updated.

10.0 REVIEW OF DOCUMENT

10.1 This procedure shall be reviewed every three years or earlier. Early review ofthis procedure shall occur in response to changes in:10.1.1 Legislation; Australian Standards, Codes of Practice; and/or10.1.2 OHSR Management System and/or10.1.3 National Self Insurer OHS Audit Tool10.1.4 OHS Act 2000 No4010.1.5 OHS Regulation 200110.1.6 Code of Practice Excavation Work 31 March 200010.1.7 Guide for Front End Loader and Excavator drivers a WorkCover NSW

publication

Unique Document

Number: S2 OHS 17


Guidelines


Manager

Reference: 6841e

PRD10/171


EXCAVATION WORK GUIDELINES

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