British Columbia CONSTRUCTION CRAFT WORKER APPRENTICESHIP PROGRAM …€¦ · · 2017-07-06Competency E1: Prepare Site ... CONSTRUCTION CRAFT WORKER APPRENTICESHIP PROGRAM 7 COMPETENCy

British Columbia

CONSTRUCTION CRAFT WORKERAPPRENTICESHIP PROGRAM

Local 1611

LINE E: Perform Site Work

LEVEL 1

CONSTRUCTION CRAFT WORKER APPRENTICESHIP PROGRAMLEVEL 1

Line E: Perform Site Work

Acknowledgements & Copyright Permission© 2017 Industry Training Authority

This publication may not be reproduced in any form without written permission by the Industry Training Authority.

Version 1 January 2017

The Industry Training Authority is under a licensing agreement with LiUNA (Labourers International Union of North American) Local 1611 to use their Construction Craft Workers Level 1 and Level 2 training materials throughout British Columbia and Canada. The Industry Training Authority would like to thank LiUNA for making these materials available.

Construction and Specialized Workers Training SocietyThese materials were initially developed for the first classes of Apprenticeship.

Level 1 by the Construction and Specialized Workers Training Society (CSWTS) in January of 2015 (British Columbia).

Those originally responsible for the manual:

• Manuel Alvernaz; Chairman of the Construction and Specialized Workers Training Society (CSWTS)

• Fred Webber; PID, Red Seal Journeyperson, Administrator and Senior Instructor (CSWTS)

• Tom Miller; PID, Red Seal Journeyperson, Instructor (CSWTS)

• Jeffrey Anders; BSc, BA, Red Seal Journeyperson, Special International and Trifunds Representative (LIUNA)

Open School BCSolvig Norman, Project Manager Monique Brewer, DirectorJennifer Riddel, Manager of Instructional ServicesDennis Evans, Production Technician (print layout, image researcher, photographer & illustrations)Max Licht, IllustratorAndrei Antica, photographerShannon Sangster, Office Manager (copyright permissions)

Copyright PermissionWikimedia Commons: Bris d aqueduc - rue Saint-Jacques - 10.jpg - Author: JeangagnonSome images were licensed from Thinkstock.

CONSTRUCTION CRAFT WORKER APPRENTICESHIP PROGRAM—LEVEL 1 3

ContentsForeword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Program Outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Competency E1: Prepare Site . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Bring site to working condition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9Hazard assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10Setting up site facilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10Safety equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Competency E2: Perform Ground Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13Locating underground utilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13Excavation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16Backfill and compaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18Guiding operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Competency E3: Perform Demolition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21Demolition techniques. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21Dismantling components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23Oxy-fuel cutting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Competency E4: Apply Excavation and Shoring Practices . . . . . . . . . . . . . . . . . . . . . . . . 39Blasting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39Tools and equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42Soil grades . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47Sloping and benching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49Backfilling and compaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

Competency E5: Service Site . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57Cleaning a site . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57Cleaning jobsite facilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61Control water runoff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65Temporary lighting and power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68Site restoration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70Tool crib attendant duties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71Recycling materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

4 CONSTRUCTION CRAFT WORKER APPRENTICESHIP PROGRAM—LEVEL 1

DisclaimerThe materials in these Learning Guides are for use by students and instructional staff, and have been compiled from sources believed to be reliable and to represent best current opinions on these subjects. These manuals are intended to serve as a starting point for good practices and may not specify all minimum legal standards. No warranty, guarantee or representation is made by the British Columbia Industry Training Authority or the Queen’s Printer of British Columbia as to the accuracy or sufficiency of the information contained in these publications. These manuals are intended to provide basic guidelines for Construction Craft Worker practices. Do not assume, therefore, that all necessary warnings and safety precautionary measures are contained in this Competency and that other or additional measures may not be required.

Safety AdvisoryBe advised that references to the Workers’ Compensation Board of British Columbia safety regulations contained within these materials do not/may not reflect the most recent Occupational Health and Safety Regulation. The current Standards and Regulation in BC can be obtained at the following website: http://www.worksafebc.com.

Symbol Legend

Important: This icon highlights important information.

Poisonous: This icon is a reminder for a potentially toxic/poisonous situation.

Resources: The resource icon highlights any required or optional resources.

Flammable: This icon is a reminder for a potentially flammable situation.

Self-test: This icon reminds you to complete a self-test.

Explosive: This icon is a reminder for a possibly explosive situation.

Safety gear: The safety gear icon is an important reminder to use protective equipment.

Electric shock: This icon is a reminder for potential electric shock.

CONSTRUCTION CRAFT WORKER APPRENTICESHIP PROGRAM—LEVEL 1 5

ForewordConstruction Craft Workers, also known as labourers, work mostly on construction sites. Their tasks include:

• Site preparation and cleanup.• Set up and remove access equipment.• Work on concrete and masonry, steel, wood and pre-cast erecting projects.• Handle materials and equipment• Perform demolition, excavation, and compaction activities.• Ensure site security.

Construction Craft Workers (CCWs) work on a wide variety of structures such as residential, commercial and industrial buildings, as well as hydro-electric dams, roadways, bridges and railways. In some jurisdictions, they also work on utility, landscape, and pipeline projects. CCWs work for private companies as well as municipal, provincial, and federal governments.

With experience, CCWs who complete additional training specialize in different areas of construction. This includes operating off-road vehicles, drilling and blasting, diving, tunneling, rock scaling, performing emergency rescue, and the management of pedestrian and vehicular traffic in situations involving potential hazards and public trust.

CCWs work primarily outdoors in all weather conditions. They are often required to work at heights, over water, in confined spaces, and excavations. Their job settings are in densely populated urban settings or in remote locations. They often work overtime during peak construction periods.

Key attributes for CCWs are mechanical aptitude, manual dexterity and an ability to do hard, physical work. They must also be able to work as team members and to interact directly with the public where such considerations as safety and legal liability are issues. Organizational leadership and blueprint reading skills are assets for anyone wanting to progress in this trade. With experience and training, CCWs can advance to supervisory/foreman positions.

Program OutlineLevel 1Line A: Use Safe Work PracticesLine B: Organize WorkLine C: Use Tools and EquipmentLine D: Perform Routine Trade ActivitiesLine E: Perform Site WorkLine F: Use Scaffolding and Access EquipmentLine G: Perform Concrete WorkLine I: Perform Utilities and Pipeline TasksLine J: Perform Roadwork

Level 2Line A: Use Safe Work PracticesLine B: Organize WorkLine D: Perform Routine Trade ActivitiesLine E: Perform Site WorkLine F: Use Scaffolding and Access EquipmentLine G: Perform Concrete WorkLine H: Perform Masonry WorkLine I: Perform Utilities and Pipeline Tasks


CONSTRUCTION CRAFT WORKER APPRENTICESHIP PROGRAM 7

COMPETENCy E1 LINE E: PERFORM SITE WORK

COMPETENCY E1

Prepare SiteConstruction Craft Workers are the first and last workers on a construction site. They clear sites of all unnecessary materials and set up temporary facilities and utilities, allowing other trades to perform their tasks. This is called mobilization.

Site layout is done to locate existing utilities and to assess pre-existing site conditions. Legal land surveyors lay out the boundaries of the project and any rights of way for roads, railways and pipelines within the project. The construction surveyor then takes control of the site layout and is responsible for placement of equipment, materials and structures until the end of the project.

Figure 1 — Surveying a site

Clearing involves heavy equipment, multiple workers on site, falling of trees and materials, and hazardous materials therefore it is important everyone coordinates and follows regulations. Refer to the OH&S Regulations, Part 16: Mobile Equipment, Part 20: Construction, Excavation and Demolition, and Part 22: Underground Workings for more information.

Figure 2 — Clearing a site

8 CONSTRUCTION CRAFT WORKER APPRENTICESHIP PROGRAM

LINE E: PERFORM SITE WORK COMPETENCy E1

Safe work permits must be in place before the work starts, otherwise fines and sanctions could be issued upon the contractor performing the work. Safe work permits are mandatory for work in proximity to steam, water and electrical lines, and may be required for other types of work.

Some areas on site must be protected before work is performed. Clearing crews must ensure that work does not contaminate streams, creek beds, roads, or any other areas adjacent to the job site. Contamination of waterways or storm sewers with organic material, dirt or debris will involve authorities. Dirty or debris-covered roadways can cause conflict with drivers and neighbours of the job site.

Besides waterways, other areas may be protected and fenced off prior to clearing to prevent any alteration or damage. Extra precautions may be required to protect trees and surrounding environment to avoid significant setbacks and financial issues.

CCWs clearing a site must also watch out for utilities. Existing utilities are located by the surveyors and marked with colour-coded flags, markers, and paint. CCWs use the coloured markings to identify buried utilities before beginning excavation work. The following table shows the international colour-code for buried utilities.

Red Electric power lines, cables, conduit, and lighting cables

Orange Telecommunication, alarm or signal lines, cables, or conduit

YellowNatural gas, oil, steam, petroleum, or other gaseous or flammable material

Green Sewers and drain lines

Blue Drinking water

Purple Reclaimed water, irrigation, and slurry lines

Pink Temporary survey markings, unknown/unidentified facilities

White Proposed excavation limits or route

Figure 3 — Utility colour legend



Bring site to working condition One of the main jobs when clearing a site is getting rid of existing materials along the surface that conflict with the work to be done. This is usually referred to as bringing the site to working condition.

Almost all construction sites contain some debris which needs to be removed safely and in a manner that it does not mix with the soil or gravel. Often, multiple bins are required for the proper disposal of brush, dirt and rocks, and paving materials.

Clearing brushBrush and organics interfere with construction processes and can cause visibility issues. It is best practice to get rid of all of it before the work starts.

Moving dirt and rocksDirt, soils, and rocks can sometimes be re-used if they are the proper classification and have not been cross-contaminated with other soils. Usually they are neatly piled to be hauled off site.

Stripping asphalt and concreteMany sites have asphalt or concrete surfaces on site, which may not mix with soil when digging the underground utilities or pilings. These need to stripped and piled neatly on site and disposed of.

Figure 4 — Stripping concrete and fill

The different materials are disposed of at their proper disposal sites.



Hazard assessmentAt the start of any job and at the start of each day, a pre-job hazard assessment should be performed by the entire crew. Having operators, drivers, foremen and labourers all understanding the daily tasks and current hazards significantly diminishes the chance of injury. A Job Safety Analysis Worksheet or other record is completed to review the hazards.

JOB SAFETY ANALYSIS WORKSHEETTitle of Operation: SOP/SWP No:

Position/Title: (Person who does job) Building:

Department: Section:

Basic Steps Potential Hazards Procedure Steps Safety Precautions

Prepared by: Date:

Approved by: Date:

H&S Rep/Committee Reviewed: Date:

Next Review Date < 5 yrs:

Figure 5 — Hazard assessment sheet

Setting up site facilitiesFacilities are set up on site in a location where they are on a level plane, easily accessible to workers and where they will not require to be moved throughout the construction process. Large and important facilities are drawn on plot plans, but small and less permanent ones may not be shown.

Site facilities may require temporary utilities such as water, sewer, electrical and communications. Pre-existing utilities are taken into consideration when a plan is designed for the temporary utilities. Do not install new utilities or alter existing ones unless you have the proper permits and have gone through the proper channels.



Facilities may include:

• Work and warehouse trailers

• Lunch rooms

• Washrooms

• First aid trailer

• Temporary fuel storage

Figure 6 — Site facilities

Refer to OH&S Regulations Part 4 & Part 5 for information on the setup of site facilities and storage of hazardous materials.



Safety equipmentPreparing a site also includes setting up safety equipment in the site facility and around the site. For more information refer to Line A: Use Safe Work Practices.

Air horns, fire extinguishers, eye wash stations, and first aid kits should be accessible at various areas dictated by the size and configuration of the job site. Safety equipment locations must be clearly defined, in proper working order, and readily accessible. Safety equipment is placed set up in first aid stations, and may also be in site trailers, foremen’s vehicles, heavy machinery, muster stations or any other hazardous areas.

Figure 7 — Muster station signage

Set up of site facilities may also include other equipment. For example:

• Tables, chairs, refrigerators and office equipment within site trailers

• Shelving and racking

• Prefab stairs or connecting platforms to trailers

Always consult the foreman and any manufacturer’s guides for information about where and how site facilities should be set up. Do not operate machinery if you do not hold the tickets for it.



COMPETENCY E2

Perform Ground Work

Locating underground utilitiesUtility location is the process of identifying and labeling underground utility mains. These mains may include lines for electricity, natural gas, telephone and communication lines, fiber optics, traffic and street lights, storm and sanitary mains, and water mains. In some locations, major oil and gas pipelines, national defense communication lines, mass transit and rail and road tunnels may also be underground.

Underground utilities must be located precisely to ensure proper clearance. Surveyors use different detection methods based on the type of material of the utility. Metal pipes and cables are located with an electromagnetic transmitter and a receiver. Plastic or concrete pipes are located with radiolocation or ground-penetrating radar. Locations of underground utilities are marked with colour-coded flags, markers, and paint.

Figure 1 — Utility indicator ribbon

Ground work within a public roadway, provincial highway right-of-way or utility right-of-way may require an excavation permit or written permission. For installing new facilities, line assignments may have to be obtained from the authority which has jurisdiction over the right-of-way.

Safe work permits are issued when work involves steam, water, air or electricity. Safe work permits are also needed when repair or maintenance work requires locking out energy sources.

OH&S Regulations require that all buried utilities which may be affected by ground disturbance must be identified and their horizontal alignments marked before digging, whether on public or private land.



Resources to consult for underground utility locations include:

• BC One Call

• Signs or markers in the area

• Land title offices

• Up-to-date “as build” blueprints

• Visual evidence of cut lines, changes in vegetation, land depression or scarring

• City utility records

BC One Call is the best way to find out what is buried on site and which areas must be avoided when digging. It is the objective of BC One Call to eliminate the risk of accidents where digging or excavation work strikes buried utilities such as pipelines, telecommunication cables, water and sewage lines, and electrical wires. Within three days of a request for information, BC One Call sends a site plan showing the exact location of buried utilities or a technician will visit the site and provide physical markings.

Figure 2 — BC One Call

Once all utilities have been identified and located and permits are in place, the dig can begin. The proper way to expose existing utilities is by daylighting. Daylighting is a non-destructive approach to exposing utilities using equipment such as hydro-vacs. It is best practice to locate utilities using a non-destructive method first to confirm their location before starting to excavate by machine.



Figure 3 — Daylighting

Another way of locating underground utilities is by looking for different soil conditions. Often when a utility is installed, the material used to backfill the trench is different than the surrounding soil. Operators and CCWs can often identify an old trench line based on differences in the look and stability of the soil as a result of different compaction density than the surrounding native soil.

Utilities must be exposed by hand and visible before mechanical equipment is used within the hand-exposed zone. The hand-expose zone stretches one metre to each side of most utilities, and five metres to each side of high pressure pipelines.

Hand Expose Zone Hand Expose Zone Hand Expose Zone

1 metre

1 metre

1 metre

1 metre

5 metre

s

Locate m

arks

Locate m

arks

Locate m

arks

5 metre

s

High pressurepipeline

Figure 4 — Hand-exposed zone



ExcavationThere are two types of excavations: trenches and bulk excavations. A trench is a narrow excavation that is 12 feet wide or less and is below ground level. It is generally used for underground utility installations. Workers must be protected from the banks collapsing. A bulk excavation is any excavation greater than 12 feet wide and is generally wider than it is deep.

Before excavating, check that the plans and drawings are the newest revision number. Clear away organic materials such as trees, roots, stumps, sod, weeds, and debris. All topsoil must be removed and piled away from the excavation. Unwanted material and debris should be hauled off site or piled away from the digging site. The area may need to be leveled off for machines to dig properly. Cut-off ditches may need to be dug in order to prevent water from draining towards the excavation. Utility locations must be identified. Weeping tile or well points may need to be placed around any foundations or the perimeter to direct ground water away.

Types of soilThere are 5 basic types of soil, based on the size of the grains of soil.

GravelGrains larger than 0.08 of an inch. Gravel includes cobble (grains larger than 3 inches) and boulders (grains larger than 10 inches).

SandGrains smaller than 0.08 of an inch but larger than 0.003 of an inch. It is a loose granular substance, typically pale yellowish brown.

SiltGrains smaller than 0.003 of an inch and larger than 0.002 of an inch. Silt has no plasticity. It can feel like rock flour and has no strength.

ClayGrains less than 0.0002 of an inch and contains a suspension of fine particles in liquid, which causes plasticity. Clay has a tendency for volume changes: it swells, softens, shrinks and dry-cracks, so it is a poor material for backfill.

Organic MaterialDisturbed soil or topsoil, including peat and loam. This material is usually removed during the excavation process because it is unstable to build on. It is referred to as overburden.

Soil gradation is a classification of the distribution of particle sizes of a soil. Coarse-grained soils like gravel or sand are graded as either well graded or poorly graded. Well graded soil contains a broad range of grain sizes, and compacts well because small particles nestle into the gaps between large particles. Poor graded soil contains a limited range of grain sizes so there is lots



of air space between particles. Gap graded soil is a type of poorly graded soil that contains both coarse and fine particles but lacks the intermediate ones.

Well graded Poorly graded Gap graded

Figure 5 — Soil gradations

The angle of repose of soil is the steepest angle of descent of the slope, relative to the horizontal plane. At this angle, the material on the slope face is on the verge of sliding. For excavations, it is the angle at which the vertical wall is cut away to support a safe trench, typically 29° to 45°.

3

4 4

3

Figure 6 — Angle of repose

An excavation needs to be dug to sub-grade, the native material underneath a constructed road, pavement, or other excavation. The sub-grade must be compacted and stable before construction because it needs to carry the weight of all materials plus the eventual pressure loads that will be placed on top. Preparation for construction includes removal of surface vegetation, topsoil and creation of space for the upper layer of the pavement. Sub-grades are tested in the field with a proctor test before any anything is placed on it.

Part 20 of the OH&S Regulations must be referred to and strictly followed regarding sloping, shoring, and excavated materials.



Part 20.79 Underground utility services(1) Before excavating or drilling with powered tools and equipment, the location of all

underground utility services in the area must be accurately determined, and any danger to workers from those utility services must be controlled.

(2) Excavation or drilling work in proximity to an underground utility service must be undertaken in conformity with the requirements of the owner of that utility service.

(3) Pointed tools must not be used to probe for underground petroleum and electrical utility services.

(4) Powered equipment used for excavating must be operated so as to avoid damage to underground utility services, or danger to workers.

Before setting foot into any excavation, workers should have a safe means for temporary access (way to get in) and egress (way to get out.) Usually, this is using a ladder. An employer must ensure that for work in a trench that is more than 1.5 m deep, there is a safe point of entering and leaving located no more than 8 m (25') from every worker. This means ladders must be placed 16 m apart so that a worker is always within 8 m of a ladder.

As an excavation progresses, measurements are constantly taken using grid lines, batter boards, tape measures, survey equipment, and various other tools. Do not over-dig in width or depth. If material is over-dug, it has to be replaced and compacted which does not give it the same structural qualities that it originally had. This can be costly and problematic. Measuring and establishing grades for specified slopes and footings is important to ensuring that they are placed in the proper location.

Backfill and compactionBackfilling is refilling an excavation. Material that has been removed during excavation can be used for backfill and compaction only if deemed to be acceptable by a geo-technical engineer. Otherwise, different material needs to be brought in due to its soil classification, moisture content and structural integrity. Some possible materials are gravel, sand, or fillcrete. Fillcrete is a flowable fill material consisting of sand and cement mix (typically 1% cement), used in excavations and trenches requiring compaction in very tight areas.

Bulking is the expansion of excavated material to a greater volume than that of the excavation from which it came. Material pulled out of a trench and piled by a machine tends to bulk because air gets mixed in between the soil particles. The opposite of bulking is compaction, process in which the air gets squeezed out of the spaces between the soil particles. Backfilled material goes back to its original state after compaction but the density is usually not the same as before.



The type of material used for backfill is important. Sand is a common backfilling when covering over utilities, and gravels are used on top of the sub-grade when building a road. Geo-technical engineers dictate what type of backfill should be used. Organics should not be used as backfill anywhere other than landscaping areas.

It is important that the right amount of backfill is placed and ordered. The volume of the excavation is calculated and then extra volume is added, based on a soil-type specific compaction factor. It is always best practice to order extra, especially if there are other areas on site where that material can be used later. Having too much material is often a smaller problem than not ordering enough.

Testing is done on backfill that will carry a load. A nuclear density gauge test is performed on site to measure the moisture content and compaction of the material. Moisture is important because a certain amount is needed to make gravels and soils bind together, while too much moisture can cause the material to become saturated. If it is too dry, it should be watered during compaction. If it is too wet, water may be allowed to evaporate over a day or two.

With some utilities like electrical and communication lines, warning tape is placed over top during backfilling. The placement height above the utilities varies based on the engineer’s requirements. When the ground is disturbed in the future, the tape acts as a warning that there are lines buried below.

Figure 7 — Utility warning tape

Backfilling is also used when installing a shoring cage or trench shield to keep the shoring cage plumb. If the cage cannot sit tight against the trench walls, the outside of the shield needs to be backfilled so that in case the trench does cave, it doesn’t cause the shield to tip over and injure the workers inside.

Guiding operatorsConstruction craft workers guide machine operators during the backfilling and compaction process. Operators do not have the same vantage points as CCWs. Direct the operators when backfilling or compacting around utilities, when placing backfill up to measured heights, when the compaction equipment has failed to sufficiently compact an area, or during any other operations where an operator is not able to see.



When backfilling around and covering utilities, the CCW has a close up view of the work area and the painted markings where the utility lies. They guide the machine operator to bring in the backfill and compact the bottom side of the utility. Next, a different gravel or sand is placed by the operator to cover the utility to help protect it and to help identify its trench line. The compaction equipment operator then compacts evenly on each side of the utility and additional backfill is placed over the utility and surrounding backfill.

Operators need to be guided when backfilling and compacting in lifts, which means backfilling up to measured heights. If the predetermined acceptable lifts are 1.5 m, then it is up to the equipment operator and crew to make sure that the lifts are 1.5 m in thickness. This involves constant communication during backfilling as well as measuring the lifts. Preparing for the lifts by painting marks on the trench walls for the top of each lift is a good practice, but only if proper shoring is in place for the CCW to enter the trench. If shoring is not in place, no worker should enter a trench and all measurements need to be taken from the ground level. Lift thicknesses must be followed so that compaction rates are met.

Once most of backfill has been placed, it is important to pay attention to the design thickness of the base materials. Each road will have different specified thicknesses of the base materials and the pavement or concrete that is to be placed on top. Most roads call for a sub-base material, a base material and then the asphalt or concrete on top. If the sub-base thickness is 0.2 m, the base thickness is 0.1 m and then asphalt is 0.1 m, then the total thickness of gravels and asphalt is 0.4 m. That means when backfilling, it is important to build the backfill up higher than 0.4 m from the surface, compact the material and then measure it. If the sub-grade is higher than 0.4 m from the surface then it needs to be cut down to grade. If the sub-grade is lower than 0.4 m from the surface then more sub-grade material needs to be added and compacted.

Figure 8 — Road cross-section



COMPETENCY E3

Perform Demolition

Demolition techniquesMany techniques are used for demolition, depending on the material and size of the structure:

• Explosives

• Ball and crane

• Pneumatic and hydraulic breakers

• Cutting

• Water-jetting

• Thermic lance

• Oxy-acetylene

• Plasma arc cutting

Figure 1 — Thermic lancing

There are also many rules and regulations that need to be met when involved with demolition. See Part 20 for OH&S Regulations related to demolition.



Cutting is a common job task in demolition. Different construction materials require different tools and techniques for cutting, including:

• Steel – all purpose saw, oxy-acetylene cutting

• Concrete – concrete saw

• Bricks/concrete – all purpose diamond saw

• Asbestos – sawzall, hand tools, scrapers

• Wood – skill or reciprocating saw, jig, hand, table, chain

• Plaster – all purpose saw with masonry blades

Figure 2 — Concrete saw

Saws may require specific blades to make cutting more efficient:

• Bi-metal blade is used, depending on the quality, for straight and quick cutting or general cutting of metal, plastic, laminates and wood with nails.

• Wood cutting blade with special teeth for ripping through lumber.

• Carbide-tipped blade for cutting bricks, porous concrete, fibreglass, plastic laminates, cement board, plywood, cast aluminum, rubber and hardwoods.

• Carbide grit blade for precision cutting of extremely hard materials (glass, glazed tiles, ceramics, fibreglass, cast iron, clay pipe, stone, bricks, plaster and marble).

Cutting materials involves many hazards which vary with the type of material and type of cutting method. Ensure you get training in using hand and power tools, and use the required PPE and safe work practices to prevent injury from electrical, kickback, point of operation, noise, vibration and dust hazards.



Figure 3 — Carbide tipped blade with heat expansion loop

Oxyacetylene and plasma arc cutting are demolition processes that have additional hazards such as hot metal and flying sparks, light rays that can burn eyes, and the production of fumes, gases, and chemical agents. Spark control is a must when cutting materials.

Dismantling componentsDismantling and removal of components should be done in a sequence that is safe and efficient for all trades and sub-trades. Dismantling and demolition must be coordinated with everyone on site to keep productivity high and to mitigate hazards.

Chutes and bins should be set up on site for proper disposal. Garbage bins are set up on ground level to keep the site clean and clear of debris. There may be separate bins for drywall or other materials that cannot go in the regular garbage. At high elevations, a crane or other mechanical device will place smaller waste bins in the upper work areas so workers don’t throw debris down to the ground.

During demolition work, proper dust control must be in place to protect all the workers on site.

WateringApplication methods include sprayers, hoses and water trucks. Frequency of application will vary with the site conditions.

CoveringsWind sheltering may be placed around work or garbage areas. Storage piles should be located downwind from workers whenever possible.

Chemical stabilizersBest applied on debris piles before forecasted windstorms, or on those that will not be disturbed much.



Before demolition, workers may be asked to lock out utilities such as water and electrical and to test electrical systems. Be aware of specific valves, pipes and circuits to know which ones need to be turned off. This information is available from the site authority or site maps.

Oxy-fuel cuttingFuel cutting is a method of cutting metals using oxygen and a fuel. Acetylene and propane are the two most commonly used fuels. Acetylene is generally used for fusion welding and flame cutting. Propane is used for heating the metal and can also be used for cutting, but with a different technique.

Oxygen is required in oxy-fuel cutting as it combines with the fuel to produce the heat during combustion. Oxygen is hazardous because it accelerates burning rapidly and raises the combustion temperature of fuel gases, which can be hazardous if the oxygen content is above standard atmospheric levels (20.8%). Under WHMIS provisions, oxygen tanks must be appropriately labeled, stored and handled using specific safe work procedures.

Acetylene gas generates high heat when it is burned. When it is proportionately mixed with oxygen, as in the oxyacetylene gas welding process, the resulting flame can reach 3300°C. This is the highest flame temperature derived from the combustion of two gases, making the combination of oxygen and acetylene useful for welding.

It is important to treat all mixtures of oxygen and acetylene as potentially explosive. Acetylene can quite easily be detected. The moment you smell it, extinguish all open flames immediately and ventilate the room even before turning on a light switch. Then test for leaks in the lines by brushing soapy water on suspected joints or areas. Watch for bubbles. Never test for leaks near an open flame.

Propane gas is supplied in liquid form in low-pressure cylinders for easy and safe handling. It is widely used because of its ability to produce clean cuts at relatively low cost. Propane has a high heat value, but requires 4.5 volumes of oxygen to one volume of fuel to produce a neutral flame. The flame temperature is 2540°C.

Cylinders, valves and safety devices The oxygen cylinder has a screw-on protective cap protecting the cylinder valve. The cylinders and protective caps are usually black, although they may be green or other colors. The caps and all other oxygen fittings have right-hand threads and come in various sizes to match the cylinders.

Because the oxygen cylinder valve is designed to operate at high pressures, it is equipped with safety features. The double seal construction prevents leakage of oxygen around the stem when the valve is completely opened. This cuts off any oxygen travelling up the stem. The regulator outlet fitting has a standard external thread to which all standard oxygen pressure regulators may be attached. Before attaching the regulator, the valve should be cracked to remove any dirt that may have lodged in the passage to the regulator.



Temperature changes significantly alter the pressure of a full oxygen cylinder. A pressure or rupture disc in the valve bursts and releases oxygen into the air when excessive pressure build-up occurs, such as from an increase in temperature.

Monitor the amount of oxygen in the cylinder. When the flame is no longer consistent and the working pressure cannot be maintained, remove the cylinder from service. Never attempt to repair a damaged valve. Tag the cylinder to indicate the fault, move it to an open area and immediately notify the supplier.

The acetylene cylinder is a strong, welded steel container completely filled with a porous material such as asbestos, charcoal or balsa wood. This filler material is saturated with acetone, a straw-coloured, stable liquid that is flammable, volatile and strong smelling. Acetone has the ability to absorb acetylene gas and is used in the cylinders to make them safe at high pressures by stabilizing the acetylene. Because the acetone is in liquid form, acetylene cylinders must be used in an upright position; otherwise the acetone may flow into and contaminate the regular, hose, torch and flame. When the flame is inconsistent and the working pressure cannot be maintained, remove the cylinder from service.

Valve

Fusible plugs

Fusible plugs

Porous filler material

300 mm (12")

Wall thickness3 mm (1 ⁄8")

Felt �lter

1075

mm

(43"

)

Figure 4 — Acetylene cylinders

Unlike the special double seal design of the high-pressure oxygen cylinder valve, the acetylene cylinder valve has a simple construction to accommodate the relatively low pressure. The valve is opened with a removable wrench or hand wheel. It should be slowly opened ¼ to ½ turn and the handle should be left in place in case it must be shut off quickly. When the handle is turned counter clock-wise (opening it), pressure is released from the seal, allowing acetylene to flow to the regulator. Safety devices for the acetylene cylinder consist of fusible, heat activated plugs threaded into the top and bottom of the cylinder. Excessive heat causes these alloy plugs to melt, which in turn releases the cylinder contents. The average range of melting temperatures for these plugs is 104°C–115°C.



Storage and handling of cylindersThe flammable and explosive properties of gases used in cutting and welding make safety procedures essential at all times. Fuels in cylinders are usually liquids. When the cylinders are shipped full, there is a space above the liquid for gas (vapor) to occupy. When the cylinder valve is opened, gas escapes, reducing the pressure on the liquid. This allows the liquid to evaporate more gas. Because they contain liquids, they must be used in an upright position.

In the storage area, cylinders should always be secured to a stationary object such as a wall to keep them from falling down or being knocked over or damaged by falling objects, passing vehicles or people. Storage areas should be well-ventilated, away from any sources of heat, salt, corrosive chemicals or fumes. Full cylinders should be stored separately from empty cylinders. When a cylinder is empty, it should be marked “MT”. Each type of gas should also have its own separate storage location.

During work, keep oxygen and acetylene cylinders as far away as possible from sparks, flame, and electrical wires. Never weld directly over cylinders. Since heat will cause pressure build-up, never use a flame or boiling water to loosen ice or snow on a cylinder valve; use warm water instead. Post warning signs to inform persons that smoking or using other sources of ignition are not allowed in the area.

To prevent a serious explosive reaction, oily and greasy substances must be kept away from oxygen cylinders, valves, hoses and fittings. Do not use oil or grease to lubricate regulators, torches, cylinder valves or other oxy-fuel gas equipment. Do not use leaky acetylene cylinders. If a leak is detected, move the cylinder to an area with good ventilation.

When work is finished, cylinder valves should be closed and protective caps put on before cylinders are moved or stored. Special cylinder carts should be used for moving cylinders, and the cylinders fastened securely. Never allow cylinders to bump together or tip over because they could explode. To transfer cylinders to and from higher elevations, a suitable cradle or box that has been certified and rigged by qualified personnel is the only acceptable method.

When using and handling oxyacetylene equipment, the following safety measures must be in place:

• Work area must have a fireproof floor. Concrete floors are recommended.

• Heat-resistant shields, such as fire blankets, should be used to protect nearby walls or non-fireproof floors from sparks and molten metal.

• Adequate ventilation is required to prevent a build-up of oxygen, fuel gas, and toxic fumes.

• Work benches or tables used during the cutting must have fireproof tops. Fire bricks or heavy steel grating are good cutting surfaces.

• Oxygen and fuel gas cylinders must be chained or secured to a wall, bench, or cylinder cart to hold them upright and prevent them from falling over.



Figure 5 — Welding table

Oxygen and acetylene regulatorsBecause of the difference between the pressure of the stored gas and fuel in the cylinders and the working pressure of welding or cutting operations, a regulator is required to control pressure for safe and effective operation. When cylinders of gas come from the supplier, they do not have regulators attached. On the job, the welder chooses the correct regulator for the type of fuel gas and type of service.

Most regulators have two calibrated gauges:

• The gauge with the higher numerical calibrations indicates the pressure inside the cylinder. It is positioned on the same side as the cylinder connection.

• The gauge with the lower numerical calibrations indicates the working pressure you select. It is on the same side as the hose connection.

A selected safe working pressure is set by turning the pressure-adjusting screw on the regulator. Turning it clockwise increases the working pressure. Turning it counter clockwise reduces the working pressure.

The oxygen regulator is always equipped with right-hand thread connections and the acetylene regulator is always equipped with left-hand thread connections. The difference prevents installing the wrong regulators.



Oxygen regulators can be identified by the following features:

• Right-hand thread connections.

• Cylinder pressure gauge calibrated from 0–4000 psi.

• Working pressure gauge usually calibrated from 0–200 psi but it may read up to as much as 1000 psi for heavy welding.

• The word “Oxygen” is printed on the regulator body and on one or both gauges.

Figure 6 — Oxygen regulator

Acetylene regulators can be identified by the following features:

• Left-hand thread connections.

• Cylinder pressure gauge calibrated from 0–400 psi.

• Working pressure gauge calibrated from 0–30 psi with a warning line from 15–30 psi.

• The word “Acetylene” printed on the regulator body.

Figure 7 — Acetylene regulator



Hoses and oxy-fuel fittingsThe hoses for oxygen and acetylene are specifically designed for oxy-fuel applications. Hoses consist of two or three layers of rubber, with a layer of strong fabric between each rubber layer for reinforcement. The outside layer may be plain or ribbed. Oxygen hoses are black or green and fuel hoses are red.

Figure 8 — Oxy-acetylene hoses

To avoid serious explosions or fires, only use hose in good condition. Faulty or damaged hose should be repaired or replaced immediately. Hose should be coiled, tied, or stored to avoid kinking. Never expose hose to oil, grease, cleaning solvents, gasoline, paint or contaminants of any kind and keep hoses away from direct sunlight.

All fittings and connectors used in the hookup to the regulators or torch body are made of a brass alloy. This prevents sparks if the fittings should accidentally bang against another metal or material. Also, brass alloy fittings will not corrode or produce any dangerous by-products if oxy-fuel gases come in contact with them. Hose fittings are also right-handed for oxygen and left-handed for acetylene to prevent switching the hose and possibly causing an explosion. A distinct groove is cut around the outside of the hex nuts on acetylene fittings as well.

Figure 9 — Oxygen and acetylene fittings



Torch assemblyThe torch assembly is the first point at which mixing of the oxy-fuel gases takes place. It is also the point at which the flow of gases can be adjusted for specific tasks. Although torch assemblies vary in design, they all have similar characteristics. At one end, the torch handle has gas inlets where the oxygen and fuel gas hoses are attached. The amount of oxygen and fuel entering the torch handle is controlled by separate valves.

Oxyacetylene flame is used to cut and fuse metal pieces, but cutting and fusing require different types of torch assemblies. For cutting, the torch handle has a cutting attachment. The oxygen valve on the torch handle is opened all the way and the oxygen is adjusted with the preheat oxygen valve on the cutting attachment.

When acetylene and oxygen (or acetylene and air) mix, they form a highly explosive mixture. If this mixture occurs before the exiting the torch head, it will cause a backfire or flashback explosion. This is a dangerous and uncontrolled explosion inside the torch equipment that can result in serious injury.

Figure 10 — Oxy-acetylene torch assembly

During the cutting process, the torch flame may back up into the cutting tip and make a popping sound. This is called backfire and is usually the result of the gasses pre-igniting inside the tip. The causes of backfire are obstructions of gas flow at the tip (carbon deposits, metal particles), a hot tip from overuse or being too close to the work, working pressures are too low, or a faulty connection between the torch handle and cutting attachment. A backfire causes the flame outside the tip of the torch to go out and re-ignite instantaneously. If backfire does not clear up immediately, carefully inspect the equipment, purge the lines and light the torch.

A flashback occurs when the backfire goes beyond the tip, through the hose, to the regulators. The torch handle becomes hot, black smoke and sparks come out of the tip, a squealing or hissing is heard and the fire eventually burns through the hose, resulting in fire damage or explosion. Flashback is caused by incorrect adjustment of torch valves, grossly unequal oxygen



and acetylene working pressures, a clogged tip along with excessive oxygen pressure, or failure to purge the lines before igniting the torch.

In the case of a flashback, it is imperative that you stop the flame immediately before explosion happens. Assume the worst and shut down the torch valves and cylinder valves as soon as possible. A flashback indicates that there is something wrong with the set-up so check all of the equipment and purge each line separately.

To help prevent backfire and flashback, make sure the valves on the torch and regulators are functioning properly. The tip should have a clear, undamaged orifice and reverse flow check valves should be used to prevent reverse flow in the lines. The best way to prevent flashbacks and explosions is to keep the gases separated. Regularly inspect the valves on the torch and cylinder as well as the gauges on the regulators.

Inspection cannot prevent gases flowing in reverse inside the torch or hose. A device called a reverse flow check valve (RFCV) is designed for this purpose. Check valves are compact and installed between the torch and the hose and between the hose and the regulators. A stainless steel compression spring holds the valve closed. When the operator opens the regulator and torch valves, the RFCV opens to permit normal gas flow, and then snaps shut if the flow reverses.

Figure 11 — Reverse flow check valves (RFCV) or flashback arrestors

Different check valves are used for oxygen and fuel gas. Sometimes check valves are built into cutting attachments. Note that all check valves are marked with an arrow to indicate the direction of gas flow.

Assembling an oxy-acetylene outfitRequired equipment:

• Cutting torch

• Specific wrench for the coupling

• Goggles for eye protection (4 or 5 lens)

• Leather welding gloves or hand protection

• Safety striker to light the torch



• Soapstone and straightedge for marking

• Soapy solution and brush to check for leaks

• Tip cleaners for cleaning the cutting tip orifice of the torch

• Bucket of water for controlling fire hazards and checking for leaks

• Fire extinguisher

• Leather apron, long-sleeve shirt, cuffless pants, and safety work boots

Oxygen regulator

Oxygen cylinder valve

Oxygen cylinder

Oxygen hose

Fuel gas cylinder

Flashback arrestor

Flashback arrestors

Cutting tip

Cutting torch body

Fuel gas regulator

Fuel gas cylinder valve

Fuel gas hose

Figure 12 — Oxy-acetylene outfit

To avoid accidents, the correct and organized procedure must be followed:

1. Secure the cylinders in an upright position. The cylinder cart is designed to roll easily when tilted back on the wheels, and be stable and secure when stationary. Cylinder caps should always be in place when transporting or storing cylinders.

2. Remove the caps covering the cylinder valves (Oxygen caps - red or green, Acetylene caps - black.)



3. Before attaching the regulators, crack the valves by opening them slightly and quickly closing them. This clears any dust or foreign particles from the valve outlets and any particles inside the valves will be ejected.

4. Match the regulator connections to the cylinder valve connections. Start turning the nut by hand and then tighten with a wrench. Never over-tighten fittings. Oxygen fittings have right-hand threads. Note that the oxygen cylinder valve is externally threaded on the regulator while the acetylene is internally threaded.

5. Turn the pressure-adjusting screws counterclockwise on both regulators. This closes off the regulators so working pressure gauges are not permanently damaged when high-pressure cylinder gases are allowed to flow through the valves.

6. Install RFCVs to regulator connections and tighten them. Make sure the arrow markings are in the correct direction of gas flow.

7. Connect the hoses to the corresponding RFCV. The oxygen hose must be connected to the right-hand threaded RFCV and the acetylene hose to the left-hand threaded RFCV. Never over-tighten the fittings.

8. Turn the oxygen cylinder valve wheel counterclockwise very slowly to prevent damaging the regulator. Watch the cylinder gauge. When maximum pressure is reached (the gauge needle will stop), turn the valve all the way open until it stops.

9. Turn the acetylene cylinder valve wheel or wrench counterclockwise very slowly, watching the cylinder gauge at the same time. When the pressure reaches maximum pressure (when the needle stops), turn the valve ¼–½ turn more to maintain that pressure. The small amount of turning provides for a quick closure of the valve should an emergency situation occur. Note that when adjusting the cylinder valves, working pressure gauges remain at zero.

10. Attach the RFCVs to the torch handle. Connect the hose to the RFCVs.

11. Place the cutting tip on the torch handle and hand-tighten the nut. Never use a wrench or pliers to tighten the connection as this can damage seals in the tip.

12. Adjust the acetylene to the required working pressure first. Open the acetylene torch valve no more than one turn. Turn the acetylene pressure-adjusting screw until the working pressure gauge reads 3 psi. This setting may vary, as different tip sizes and torch designs require different pressures. Next, close the torch valve gently to prevent damage.

13. Follow the same procedure to adjust the oxygen to the required working pressure of 5 psi. The torch is now ready to use.



The system is now considered pressurized from the cylinders to the torch valves and will remain so if there are no leaks. Before using the torch, check the line for leaks, whether the equipment is being assembled for the first time or the set-up is used repeatedly. The line should also be tested after any new cylinders or parts have been installed.

To quickly determine if a small leak is present, increase the working pressures to 10 psi after opening the cylinder valves. After adjusting the working pressure, close both cylinder valves again and watch the cylinder pressure gauges for pressure drop. Make sure the torch valves are closed.

If a gauge indicates a leak, use the following methods to pinpoint it:

• Listen, smell and touch around connections, hoses and fittings for a leak.

• If the leak cannot be found by those methods, apply a soapsuds solution to possible leak areas. Bubbles will appear where there is a leak.

• Repair the leak, if possible, test the system again. If cylinder pressure remains constant, the system is okay.

Lighting the torch Take a few minutes to familiarize yourself with the feel of the torch and striker while wearing gloves. Practice using striker by holding it about 1" from the end of the welding tip.

Figure 13 — Striker

As a safety precaution, always purge the torch and hose before igniting the flame, especially if the equipment was shut-down. Explosive gas mixtures may have collected inside the torch and hose. Open each torch valve, one at a time, for 5–10 seconds and then close them.

Open the acetylene torch valve no more than ½ turn and light the gas coming out of the tip with the striker. Adjust the acetylene valve until the flame becomes turbulent and stops giving off black smoke. The flame should be yellow-red.



Figure 14 — Lighting the torch

Gradually open the oxygen torch valve and adjust it to a neutral flame. As oxygen is fed into the flame, the colour changes from yellow-red to blue and a small, light green inner cone starts to form. If too much oxygen is added, the flame will hiss, the inner cone will be pointed and then metal being heated will burn or oxidize. If too much acetylene is added, the inner cone will be dark-blue and feathered, and this will add carbon to the metal.

Shutting down and disassemblingIt is very important to know how to correctly shut-down an oxyacetylene outfit once the welding is complete or when leaving the work area. A mistake could result in an injury to workers so follow the shut-down procedure exactly as described.

1. Close the acetylene torch valve.

2. Close the oxygen torch valve. Gas is no longer leaving the welding tip but the system is still pressurized. If work is stopped 10 minutes or less, the torch can be left. If it is left longer than 10 minutes, the oxygen and acetylene must be bled from the torch, hose, and regulators. To bleed lines, tightly close the acetylene cylinder valve first, then the oxygen cylinder valve.

3. Open the acetylene torch valve. The pressure headings on both acetylene gauges will drop to 0 and you will hear the acetylene gas being released from the line.

4. Turn the acetylene pressure adjusting screw all the way out, counterclockwise to close the regulator.

5. Close the acetylene torch valve gently.

6. Open the oxygen torch valve. The pressure readings on both oxygen gauges will drop to 0 and you will hear the oxygen begin released from the line.

7. Turn the oxygen pressure screw all the way out, counterclockwise to close the regulator.

8. Close the oxygen torch valve gently.



Acetylene valve handwheel

Oxygen valvehandwheel

Acetylene cylinderpressure gauge Acetylene working

pressure gauge

Oxygen cylinderpressure gauge

Oxygen workingpressure gauge

Figure 15 — Regulators and cylinders

Never disassemble equipment if the gauges do not read 0, the lines have not been bled or the cylinder valves are not tightly closed.

Disassembly procedure:

1. Disconnect the cutting tip attachment from the torch handle and store it in a container free from oil or grease. Attach a fitting to the torch handle to keep it clean.

2. Disconnect the hose from the RFCVs on the torch handle. The RFCV may remain on the torch handle unless it needs service.

3. Disconnect the hose from RFCVs on the regulators. Again, RFCVs may remain on the regulators.

4. Disconnect the regulators from the cylinder valves. Carefully place each regulator with the attached RFCV in separate containers. Regulators are precision instruments and can be damaged from rough handling.

5. Place protective caps over the cylinder valves and hand-tighten. If they are empty, they should be marked “MT” and cylinder caps should be installed.



Cutting processFollow the procedures for starting a cut in steel plate:

1. Preheat a small spot on the base metal to a bright cherry red colour.

2. Hold the tip of the preheat flame about 1/8" from the metal where the cut is to begin, with the tip angled toward the direction of the cut. Tilting the torch slightly to one side will prevent sparks and slag from blowing toward the operator.

3. Depress the cutting oxygen lever. Always use both hands to guide and stabilize the cutting torch.

4. When metal is pierced through, move the torch in the direction of the cut.

5. As the cutting starts, slowly rotate the tip toward the direction of the cut. Advance as fast as cutting will allow. Moving too fast will lose the cut and moving too slowly will cause the cut to fuse together.

6. Holding the cutting oxygen lever, continue cutting past the edge of the metal to complete the cut.

Figure 16 — Oxy-acetylene cutting




COMPETENCY E4

Apply Excavation and Shoring PracticesExcavating material is a procedure of breaking ground, removing existing material and allowing components to be installed on the excavation site. Excavations can be as small as narrow trenches and as large as major building developments and industrial sites. Whenever excavating material, many safety measures have to be put into place to perform the job properly and to keep workers safe.

There are two types of excavations; narrow and bulk. A trench is a narrow excavation which is 12' wide or less and below ground level. It is generally used for pipelines, water lines and smaller applications. A bulk excavation is any excavation wider than 12', usually larger building sites.

Figure 1 — Loading from bulk excavation

Excavating may be done by blasting or digging with hand tools or heavy equipment.

BlastingOften during an excavation, large rocks and boulders need to removed or destroyed. The boulders may be much too large to move so the rock is blasted into smaller pieces which then can be moved easily by large equipment.



Although blasting is a common practice, it can still be quite dangerous. The Blaster-in-charge will take all necessary precautions possible in calculating the size of the blasting area as well as ensuring that nobody enters the blasting area that isn’t needed there. All workers must obey safety measures around blasting activities to avoid injury or death.

Figure 2 — Drilling rock for blasting

Debris, otherwise known as fly rock can travel very fast. Workers far away from the blasting area can still be struck with fly rock, although it is less likely as they have more time to react. Blasting mats are often laid on the rock to help reduce or eliminate the hazard of fly rock.

Warning signals are used as a precaution in blasting operations. Knowing what they are and when you can expect them can save your life. Below are the blasting signals as specified in Part 21 of the OH&S Regulations.



21.69 Blasting signals(1) The blaster must ensure that an audible signalling device, distinct from other signalling

devices in the area, is used to give the following warning signals:

(a) preceding the blast, 12 short whistle signals must be sounded at one second intervals;

(b) two minutes must elapse after the last warning signal before initiating the blast;

(c) following the blast and after the area has been inspected and found safe, one prolonged whistle signal of at least 5 seconds duration must be sounded, to signify that permission is granted to return to the blasting area.

(2) Subsection (1) does not apply to avalanche control, single underground headings, buried seismic work in isolated locations or other circumstances deemed appropriate by the Board, in which case the blaster must ensure that alternative warning procedures acceptable to the Board are used.

(3) Subsection (1) (b) does not apply with respect to the 2 minute warning in congested areas if alternative warning procedures acceptable to the Board are developed and implemented.

Figure 3 — Blasting mats



Tools and equipmentShovels are used to dig, lift, or move materials such as clay, gravel, concrete, soil, etc. They have a large, almost flat, head attached to a handle. Square mouth shovels have a square head and are used specifically for shoveling sand, concrete, loose dirt, fill, gravel and crush. They are also used for clean up. Spade shovels or round mouth shovels, have a pointed head which allows for easy penetration into the ground for excavation and digging in harder materials such as clay. In excavations, they are often used in hand-expose zones around existing utilities. Track shovels have a narrow head and are used to get into hard to reach areas and to clean excavator tracks.

A clay pick (Maddox) is used to excavate hard compacted soils. Picks work well for digging trenches. Picks loosen compacted material and then spades are used to remove the material from the trench.

Figure 4 — Maddox

Wrecking bars are long straight bars, usually 5 feet in length, are used to dismantle forms or pry against large objects. Due to their weight and narrow frame, they are also ideal for excavating very narrow areas where a shovel may not fit, or there is no room to swing a Maddox.

Figure 5 — Wrecking bar



Excavation equipment is not generally operated by a labourer, but it is still important to know the types of equipment that you may come into contact with.

A loader (bucket loader, front end loader) is mostly used for moving, placing, and loading soils. The loader is a tractor usually on wheels, but can be on tracks instead. It has a front-mounted bucket that is connected to two arms. The bucket is used to pick up materials from the ground and transport them to a spoil pile or dump truck. The loader is can also be equipped with other attachments such as forks, clamshell buckets, or sweepers. Loaders are generally used for transportation and moving of materials, not usually for any excavating.

Figure 6 — Front end loader

An excavator (track hoe) consists of an undercarriage, rotating platform know as a house, a boom, and a bucket. The undercarriage includes the tracks, track frame and final drive. The house carries the operator’s cab, the counterweight, engine, fuel and hydraulic oil tanks. They come in many different sizes and are designed for digging trenches, large excavations, and holes. Track hoes can have immense power but have somewhat limited manoeuvrability.

Figure 7 — Excavator



Track hoes also have many attachments:

• Digging buckets have protruding teeth and are used for digging in harder ground

• Clean-up buckets have a flat edge and are used for digging in softer ground or cleaning purposes

• Hoe-packs are hydraulic compactors that connect to the stick that use vibratory action to compact soils

A backhoe looks like a front-end loader but also includes a boom attached to the back. The hydraulic boom is attached to a pivot which allows it to move left and right. A backhoe digs by drawing the earth towards it, rather than lifting with a forward motion like a bulldozer. The back bucket can be exchanged for attachments such as breakers, hoe-packs and various buckets, and outriggers are extended for stability when digging.

Figure 8 — Backhoe

A bulldozer is a tractor that is either on wheels or tracks with a large metal blade attached to the front. The main use of a bulldozer is to push large quantities of soil. However, it may also be equipped with a ripper at the back which loosens densely compacted materials. Most bulldozers are on tracks because tracks give them greater mobility over rough terrain.

Figure 9 — Bulldozer



A scraper is a piece of equipment that can move soil and also perform short hauls. At the back of the machine is a vertically moving hopper which has a sharp horizontal edge. The hopper lowers and cuts into the soil, and as the scraper moves forward the scraped soil fills the hopper. Once the hopper is filled and raised, it can transport the material away to be emptied.

A skid steer (Bobcat) is a small rigid framed vehicle that can be equipped with tracks, but more often has wheels. It has independent left and right drive wheels. The movement is known as skid steering as the wheels are in a non-steerable fixed position. A skid steer has a bucket attached to the arms at the front of the machine. The bucket can be removed and replaced with other attachments such as sweepers, forks and augers.

Figure 10 — Skid steer



An auger is a device that moves material by means of a rotating helical screw blade and can attach to different machines. In excavation they are designed for digging deep holes, most commonly for piles and lateral boring.

Figure 11 — Auger

A hydrovac is a system that uses water and vacuum technology to quickly and cleanly blast through dirt and rocks to expose pipelines, utilities, and electrical systems, or to open the ground for future. This is a non-destructive method of excavating around existing utilities. A high pressure jet spray of water is used to cut through the soil and a suction hose is used to extract the water and soil mixture.

No matter what equipment one might be working around, here are some general safety tips that should be met:

• Keep clear of the equipment whenever possible.

• Never assume the operator knows where you are or where you are going.

• Watch out for and steer clear of pinch points.

• If you must walk near a piece of machinery, make eye contact with the operator first before proceeding.



• Never go under loads, buckets or any other suspended items.

• Never walk on or ride on a piece of moving equipment.

Soil gradesSoils are given grades, based on the sizes of soil particles in a sample.

• Well graded material or soil contains a broad range of grain sizes. A well graded soil compacts to a higher density than a poor graded soil.

• Poor graded material contains a limited range of grain sizes.

• Gap graded material contains both coarse and fine particles but lacks the intermediate ones.

Well graded Poorly graded Gap graded

Figure 12 — Soil grades

Soil is also classified by soil type, which is based on the conditions. Soil type is used to determine what shoring materials, sloping or benching is needed.

SOIL TYPE DESCRIPTION

A Hard and solid soil (stiff and cohesive)

B Likely to crack or crumble (clay and limestone cohesive)

C Soft, sandy, filled or loose (disturbed soil or top soil)

Engineers design the specifications for a jobsite by analyzing soil samples. Well before the job starts, test holes are dug and samples analyzed for grade and soil conditions (soil type). Soil conditions may change somewhat, so adjustments would be made as required.

One way in which soil conditions may change is swell (bulking). Swell is the process of soil volume increasing due to aeration when the material is moved. For example, a hole is dug, measuring 1 yard long, 1 yard deep and 1 yard wide. The dirt is thrown into wheelbarrows. In the ground, the soil was 1.0 cubic yard in volume, but once thrown into the wheelbarrow the soil has a volume of about 1.2–1.4 cubic yards because air has been mixed in between the soil particles.



Another way in which soil conditions may change is compaction (shrinkage.) An example of compaction is if that same soil from the wheelbarrow is placed back in the 1.0 cubic yard hole and is tamped down. The final volume could be between 0.9–1.1 cubic yards, depending on how much it is compacted. This explains why when refilling a hole with the same dirt taken out, sometimes there is not enough soil to fill the hole and sometimes there is soil left over.

Protecting workers in trenching and excavationsTrenching and excavation work presents serious risks to all workers involved. Workers should never enter an unprotected trench. The greatest risk and primary concern is a cave-in. When cave-in accidents occur, they are more likely to result in worker fatalities than other excavation-related accidents. Strict compliance with all local and federal regulations and the use of best practices helps prevent accidents.

Any kind of trench deeper than 4' (1.2 m) will require some form of sloping, benching, shoring or shielding. Factors taken into consideration when determining the method of trench reinforcement include:

• Depth and width of the trench or excavation

• Soil conditions and anticipated soil pressures

• Ground water seepage and saturated or submerged soils

• Location of nearby utilities and structures that must be supported by soil near the trench

• Surcharge loads, including spoil from the trench, stored material, equipment, and traffic

• Vibration expected

• Type of excavating equipment to be used

• Working space requirements, allowing for size of material to be installed, bedding, and other factors

• The length of time the trench is to remain open

• Effect of possible changes in weather

Refer to OH&S Regulations Part 20.78 to 20.95 for information on sloping, benching, combined shoring and benching, shoring and shielding.



Sloping and benchingSloping is inclining the sides of an excavation so they have stable faces. For each classification of soil type, OH&S Regulations define maximum angles for the slope of the walls. In general, the looser the soil, the more likely it is to cave in, so the more gradual the sides have to be.

3

4 4

3

Figure 13 — Trench sloping

Benching is another method used, sometimes in conjunction with sloping. The same regulations are followed as in sloping, but rather than bank being sloped, it is cut in a stair or step-like fashion. Benching can be used whenever the space is available and can also be used to step down into very steep excavations.

1.5

11.2 m (4 ft.)Maximum



Figure 14 — Benching excavation



Shoring and shieldingProtecting workers in an excavation with barriers to the soil include trench shoring, trench shielding, and sheet pilings.

Trench shoring is a system that supports the walls of the excavation and prevents their movement and collapse. Modern shoring systems are engineered to preload trench walls (they push against the soil on the sides of the trench.)

An aluminum hydraulic shoring system may include cross brace cylinders, vertical sheets (uprights), and horizontal rails (wales). They may be used with or without backing, depending on soil conditions. Cylinder extensions can be used to adapt to various widths. Shoring does more than provide a safe environment for workers in a trench. Because it restrains the movement of trench walls, shoring also stops the shifting of adjacent soil which may contain buried utilities or support sidewalks, streets, building foundations, or other structures.

Figure 15 — Hydraulic trench shoring

Hydraulic shoring systems are quick to install, safe, and simple to use. They can be used as spot bracing for repair situations or for production trenching. They come in an array of sizes and configurations of backings and with various cylinders.



Timber shoring systems are usually constructed of dimensional lumber planks or timbers that can be used alone or can be adjusted with wood wedges. Timber shoring materials must be lumber graded Number 2 or better from the following species groups: Douglas fir-larch, hemlock-fir, spruce-pine fir, or coast-Sitka-spruce.

Figure 16 — Timber shoring

After soil conditions are classified as Type A, Type B, or Type C, the engineer refers to OH&S Regulations Part 20, Table 20.1. The table states requirements of timber shoring based on the type of soil and the depth of the excavation. The table indicates the minimum sizes of timbers in metric or imperial units and maximum spacing of the uprights, walers and cross-braces. All spacing dimensions in the tables are measured center-to-center.

Few contractors use timber shoring systems today. Some of the main disadvantages are that there is a limited availability of the timber, it is a lengthy process to build, skilled workers are needed to build the system and because workers may have to enter an un-shored trench at times while building it. However, timber shoring is still considered by OH&S Regulations to be a legal means of shoring.



Trench shield systems (trench boxes, trench shields) are steel or aluminum structures used for protecting workers from cave-ins and other external forces while performing their duties within a trench. They are normally constructed with sidewalls of varying thicknesses held apart by steel or aluminum spreaders.

Figure 17 — Trench shield system

Shields can be permanent structures or can be designed to be portable and moved along as the work progresses. Unlike shoring, the walls do not necessarily have to be braced against the sides of the excavation. However, the space between the outside of the trench box and the face of the trench must be as small as possible and backfilled to prevent side-to-side movement. If the sides of the excavation are not stable enough to stand long enough to excavate for the shield, the shield can be placed high and pushed down as material is excavated.

A single project can include several depth or width requirements and varying soil conditions. This may require that several different protective systems be used for the same site. Shields are certified to specific depths, depending on soil conditions, by a registered engineer. The certification must be available at the job site during the assembly of the shield and be available upon request after assembly.



All shoring or shielding must extend at least 1' (30 cm) above the ground level, and reach as close to the bottom of the trench as the material will allow. In no case may the bottom of the shield be greater than 2' (60 cm) from the bottom.

Other regulations that must be met when installing trench shoring and shields:

• Before excavating, the location of all underground utility services in the area must be accurately determined.

• Shoring does not need to extend above ground level where traffic crossing plates are used, provided that other measures are taken.

• Shoring materials must be installed from the top of the excavation to the bottom and removed in the reverse order.

• The removal of any type of shoring system should coincide with the backfilling of the trench.

• Unless otherwise indicated by the manufacturer or engineer, voids between the shoring and excavation face must be backfilled or blocked.

• The number of braces, spacing of braces, and dimensions of uprights, braces and walers is determined by the trench depth.

• At each cross bracing location the cross braces must be less than 4' (1.2 m) apart and the uppermost brace must be within 2' (60 cm) of ground level.

• Hydraulic or pneumatic trench jacks must have a means of ensuring that they will not collapse in the event of loss of internal pressure.

• Safe means of entry and exit must be provided for an excavation a worker enters and if it is a trench, the point of entry and exit must be within 25' (8 m) of every worker.

• Excavated material must be kept back 2' (60 cm) from the edge of a trench excavation and 4' (1.2 m) from any other excavation.

• The sides of an excavation must be scaled and trimmed or otherwise stabilized to prevent slides of material or falls of rock which could endanger workers.

• Water must not be allowed to accumulate in an excavation if it might affect the stability of the excavation or might endanger workers.



Sheet piling is a system of steel sheet sections with interlocking edges. Sheet piles are installed in sequence to design depth along the perimeter of an excavation or seawall alignment. The interlocked sheet piles form a wall for permanent or temporary lateral earth support and reduce groundwater inflow. Anchors can be included to provide additional lateral support if required.

Sheet pile walls are used to support excavations for below-grade parking structures, basements, pump houses, and foundations, and to construct cofferdams, seawalls and bulkheads. Permanent steel sheet piles are designed to provide a long service life.

Figure 18 — Sheet piling

Vibratory hammers are used to install sheet piles. If soils are too hard or dense, an impact hammer can be used. At certain sites where vibration is a concern, the sheets can be hydraulically pushed into the ground. Sheet piles are also a sustainable option since recycled steel is used in their construction, and the piles can often be reused.

Backfilling and compactionBefore construction of a structure, soil is often disturbed from its natural position by excavating, grading, or trenching. Soil compaction is the process of applying energy to loose soil, and is used to:

• Increase load-bearing capacity

• Prevent soil settlement and frost damage



• Increase stability

• Reduce water seepage, swelling, and contraction

• Reduce settling of soil

There are three major compaction methods. Static force is achieved using a heavy machine that slowly squeezes soil particles together without vibratory action, like a roller. Impact force is achieved by dropping a large mass onto the surface of the soil. Vibratory action is achieved by applying a high frequency vibration to the ground which causes soil particles to settle in closer together and interlock.

Before and during site preparation, compacted soil is measured for density, expressed in pounds per cubic foot (lb./cu ft.). The higher the number, the more dense the soil. Soil is tested both in the laboratory and in the field.

Proctor compaction tests are done in a laboratory. They measure the optimal moisture content at which a given soil type will become the most dense and achieve its maximum dry density. Using special equipment including a standardized weight and mold, soil samples of equal volume but different moisture contents are compacted in exactly the same way into three layers in the molds. The samples are weighed while wet, then dried and weighed again. Comparing the weight and volume of different samples will show the moisture content at which the soil density is the greatest.

Nuclear tests are done in the field and give results in minutes. Test results can eliminate over-compaction and determine what type of compaction procedures should be used to deal with compaction issues. Common compaction issues are soil that is too wet or too dry, the soil lifts are too deep, there are many different types of soils, or the soils inspector samples were taken at the wrong phase of construction.

Nuclear tests are fast and accurate, making them the most widely used method in the field. A portable nuclear gauge is used to measure moisture content and density of compacted soil by the interaction of gamma radiation with hydrogen atoms in the soil. Dense soil absorbs more gamma radiation than loose soil.

The nuclear gauge is placed directly on a flat surface of the test soil. Depending on the device it may or may not use a source rod. If using a source rod, a test hole is made in the soil by hammering a drill rod into the soil with a hammer to assure proper alignment. The source rod is then fully inserted into the premade hole and a reading is taken. Gamma rays (photons) penetrate the soil and a microprocessor in the nuclear gauge converts the data to display measurements for dry density, wet density, percent moisture, moisture content, percent compaction, or void information.




COMPETENCY E5

Service Site

Cleaning a siteThere are many hazardous chemicals to which a construction worker may be exposed. The most common categories of hazardous chemicals found on construction sites are:

• Acids and bases

• Adhesives and sealants

• Cleaners

• Fuels

• Solvents

• Treated wood

Figure 1 — Power washing

Acids and basesAcids and bases can easily damage the skin and eyes. The seriousness of the damage depends on the strength of the chemical, length of contact, and actions taken. Acids and bases can be liquids, solid granules, powders, vapours, or gases. Sulfuric, hydrochloric, muriatic, and nitric acids are commonly used acids. Commonly used bases (caustics) are lye (sodium hydroxide) and potash. On the pH scale, neutral is 7:

0 2 4 6 7 8 10 12 14

Acidic Alkaline

Figure 2 — Solvent PH



Cement and mortar, whether wet or dry, are base compounds. As dust and powder, they can damage the skin when they react with moisture in the body. Concrete and mortar can also cause allergic reactions in people who have become sensitive to them. Always follow these rules when working with acids and bases:

• Know what chemicals are being worked with and at what concentration.

• Use PPE required.

• In case of skin or eye contact, flush with cool water for at least 15 minutes. Do not rub the skin or eyes.

• Prevent splatter by adding acid to the water when diluting it.

• Do not mix acids with bases. Store them separately, and clean up spills promptly.

Adhesives and sealantsAdhesives and sealants always have some type of hazard warning on the label. Because people often use them at home and on the job, warnings are often taken lightly or ignored. However, adhesives and sealants are toxic due to their chemically reactive ingredients or because of the solvent base.

Adhesives or sealants that contain solvents may also be flammable. Other types of adhesives, such as caulking or wood glue, may irritate the eyes and skin. When working with any glue, avoid eye and skin contact. Use and store flammable adhesives away from sources of ignition. Epoxies contain epoxy amine resins and polyamide hardeners, both of which sensitize skin and irritate the respiratory tract. Overexposure to epoxies can cause dizziness, drowsiness, nausea, and vomiting. Extreme or prolonged exposure can damage the kidneys and liver.

Figure 3 — Caulking gun

Flooring adhesives may contain acrylics that irritate your skin and may cause nausea, vomiting, headache, weakness, asphyxia, and death. Other adhesives or sealants may contain coal tar derivatives that are suspected carcinogens. Avoid prolonged breathing of vapours or skin contact.



CleanersCleaners can contain acids, alkalis, aromatics, surfactants, petroleum products, and ammonia. Because of these ingredients, cleaners are irritants which are harmful if swallowed or inhaled. Cleaners can cause eye, nose, throat, skin, and lung irritation. Some cleaners are flammable and burn easily. Others may be caustic or corrosive and cause severe skin damage. Protection is required for these chemicals. Read the labels and SDS and follow recommended precautions. Wear gloves and eye protection, avoid inhaling the vapours and mists. Wash your hands and face thoroughly before eating, drinking, or smoking.

FuelsFuels are either flammable or combustible. Their primary hazard is fire. Fuels should be handled with care. Always store and transport fuels in approved safety containers. When filling portable containers with flammable materials, properly ground and bond the container to prevent ignition caused by static electricity. Store gasoline in containers marked “Gasoline”. Store kerosene in containers marked “Kerosene”. Never transport or store fuels in containers not intended for that fuel.

Figure 4 — Fuel container (jerrycan)

Excessive skin contact with fuels can result in dermatitis. Fuels entering the body through the skin over a long period can break down the fatty tissues and possibly build up in the body. Excessive inhalation of fuels may cause central nervous system depression and aggravation of any existing respiratory disease. Leukemia is a potential side-effect of chronic exposure. Ingestion of fuels may cause poisoning and possible lung damage. Acute exposure to fuels may result in skin, lung, and respiratory tract irritation.

Do not pour waste fuel and flammable liquids down the drain. See the MSDS or SDS for proper waste disposal procedures. When using portable containers, check that spark arresters are in place. When dispensing or using fuels, be aware of the location of fire extinguishers, fire alarms, and evacuation procedures. Fuels are flammable, so do not use or dispense near arc welding or open flame.



SolventsSolvents are liquids that dissolve another substance without changing the characteristics of either material. When solvents evaporate, the original material left behind remains the same. In construction, the most commonly used solvents are cleaners, degreasers, thinners, fuels, and glues. Solvents can be absorbed by contact with the skin, then enter the bloodstream and attack the central nervous system and other organs. Like all chemicals, effects depend on several factors: chemical toxicity, length of exposure, solvent strength or concentration, and the body’s sensitivity level.

Treated woodTreated wood is pressure-treated lumber which has been treated with a chemical to protect it from insect attack, water, sun and mould. The pressure-treatment process includes use of inorganic arsenic, copper, and zinc, called chromated copper arsenate (CCA). The combination of pesticide and chemicals are forced deep into the wood where they remain for a long time. As a result, treated wood, whether fresh from the lumber yard or found in an existing structure, can pose hazards to your health if not handled properly.

Avoid inhalation of sawdust from treated wood. When cutting, routing, sanding, or working with treated wood, wear a respirator. Whenever possible, perform these operations outdoors to avoid indoor accumulations of airborne sawdust. Keep workers and bystanders from walking in the collected sawdust. Dust control measures are applicable to any construction site where there is a potential for air and water pollution from dust travelling across the landscape or through the air. Some treated woods appear damp and have chemical residue on the surface. Use gloves when handling freshly treated lumber and especially the sawdust from freshly treated wood. Wash hands and face thoroughly. Take meals and breaks away from the work area. Separate work clothing from other clothing and wash it after each use.

Do not burn treated wood scraps in stoves, fireplaces, or open fires, because the chemicals may become part of the smoke and ashes. Treated wood is burned in commercial and industrial incinerators or boilers according to provincial and federal regulations.

Workers who use or manage chemical substances must have an understanding of the MSDS including spill control, the type of fire extinguisher required, incompatible substances, and reactivity with substances such as water or air. Unknown substances and those without an MSDS are always treated as high risk.

Spills can be prevented or controlled by containment including a raised lip at the front of work benches. Spill kits are often required on job sites. The contents of the spill kit should be relevant to the area and the potential spill. Contents may include:

• An amount of vermiculite sufficient to deal with a large spill of non-corrosive liquids.

• An amount of Sodium Hydrogen Carbonate to deal with spills of corrosive liquids.



• Bags of kitty litter, saw dust or sand to absorb other spilled liquids.

• Brooms, dustpans and a square-mouth shovel to clean up absorbent material.

• Absorbent pillows or booms to contain larger liquid spills and prevent spills from entering drains.

• Plastic bags or plastic drums to contain hazardous material for disposal.

• Appropriate PPE (chemical resistant gloves, safety glasses).

• A wheeled bin to contain all the above equipment and store hazardous material prior to disposal.

Spill kits must be clearly labeled and located in easily accessible locations for all workers. All workers must be aware of and be able to access the chemical spill management and chemical spill guidelines, and know how to use the spill kit in case of an emergency. Spill kits must be restocked following use and the contents checked on a monthly basis.

Figure 5 — Spill kit

Workers who use chemicals and hazardous materials must have a valid WHMIS ticket and all materials must have corresponding MSDS. MSDSs must be readily available for all controlled materials that are produced or used on the site. Refer to MSDS and WHMIS legislation for storage rules for each controlled material.

Cleaning jobsite facilitiesHazardous materials that a worker could come across when cleaning a site facility include asbestos, corrosive chemicals, oxidizing and bio-hazardous materials.

When working with hazardous materials and hazardous chemicals, different types of PPE are required.



Whole body protection can be fully encapsulating suits or splash suits. Fully encapsulating suits protect workers from chemical splashes, gases and vapours. They are a full enclosure. Splash suits consist of a jacket and hood in combination with a pair of pants or bib overalls. This type of suit provides protection from chemical splashes only. Duct tape is used to seal the overlap between sleeves and gloves but duct tape does not provide a true seal.

Figure 6 — Splash suit with protective booties

Hand protection is critical because hands are the most likely body part to come in contact with chemicals. It is often common to wear more than one pair of gloves. Outer gloves are used to protect expensive chemical resistant gloves from damage due to abrasion, puncture and rips. Inexpensive gloves are discarded after each use while more expensive gloves are discarded less often.

Boots made from chemical resistant materials protect the feet from chemical contact. Boot plastic is much thicker than glove material so permeation is not as much of an issue. Disposable boot covers are commonly used to minimize contamination of boots. Special boots also have spark-proof bottoms which protect the worker from electrical hazards.

Full-face respirators are used to protect the face and eyes. However, when wearing half-mask respirators, face shields or goggles are used to protect the upper face from chemicals. The face shield must not interfere with the respirator’s seal.

Leakage is a big limitation of PPE. For respirators, leakage relates to how well the mask fits. For gloves and protective clothing, chemicals can pass through the protective barrier of the clothing.



There are three important terms to know about when discussing leakage of the Chemical Protective Clothing (CPC):

• Permeation is the process by which a chemical passes into the chemical structure of the material and through to the other side. The length of time it takes a chemical to permeate depends on the chemical’s properties.

• Degradation is the process by which a chemical changes the protective material so that it loses effectiveness as a barrier. Chemicals, sunlight, and high temperatures all can cause degradation.

• Penetration is the ability of a chemical to pass through a garment by way of openings in the material. Examples include pin holes, imperfections in the material, zippers, and seams.

Occupational health specialists working on hazardous waste sites have developed four levels for protective clothing:

Level AThe highest level of protection. Consists of a fully-encapsulating, vapour and gas proof suit with an atmosphere-supplying respirator. Used in environments with high chemical exposures and highly toxic contaminants.

Level BProvides the same level of protection as level A, but uses a chemical splash suit that provides good to moderate skin protection. Used when gases or vapour levels are not high enough to be a hazard to the skin.

Level CA chemical splash suit and a full-face APR. Used when airborne chemical levels are reliably known and chemical filters are available.

Level DThe lowest level of protection. No respirator is required and skin protection is minimal.

Contamination occurs when hazardous material spreads to an unwanted location. The following conditions and actions may be sources of contamination:

• Leaks or breaks in containers or systems.

• Opening containers or systems without proper controls.

• Airborne contamination settling on surfaces.

• Poor housekeeping practices in contaminated areas.

• Too much motion or movement in high contamination areas.

• Sloppy work practices that result in cross-contamination of tools, equipment, or workers.



Contamination avoidance is the process of planning to avoid unnecessary exposures. Use remote sampling and handling equipment if possible to put distance between you and sources of obvious contamination. Do not touch barrels, equipment, or debris unless the job requires you to do so. Do not sit on potentially contaminated soil, equipment, drums, etc. Do not expose yourself to liquid or solid chemicals unless it is necessary to complete the work task. Jobs may be arranged to avoid walking through areas of obvious contamination.

Figure 7 — Warning sign

Use plastic bags and sheeting to control the spread of contamination. Tools and equipment can be protected during use by keeping them in plastic bags. A plastic liner may be placed over a leaking barrel to cut down on contact with PPE or may be used to line a storage area. Disposable clothing such as Tyvek® suits can be used over chemical protective suits to keep bulk material off.

Contamination transfer is the act of passing contamination from one item, person, or area to another item, person or area. Remove PPE with care, in the order established for the decontamination procedure. Assume that all PPE is still contaminated and avoid touching it, even though it has been washed.

Figure 8 — Decontamination washdown



There are several methods for removing contamination. The most commonly used methods are physical removal and chemical removal.

Physical removal procedures include scraping, brushing, and wiping to remove contaminants. Heat may also be used to evaporate some chemicals that have entered the fabric of protective clothing. Studies have shown that airing out protective clothing for 8–24 hours can be an effective way to remove some chemicals.

Chemical removal is the use of chemicals to dissolve or loosen contaminants from material to breakdown, change, or neutralize the contaminant. Strong detergent is usually used in chemical removal. Solvents can also be used to remove contaminants by chemical action; this is how dry-cleaning fluid cleans clothes. Weak acid solutions may also be used to neutralize some caustic solutions. Great care must be used during chemical removal to be sure that damage does not occur to PPE and cause additional safety and health problems.

Three general methods for chemical decontamination of protective clothing are water and detergent washing, water and bleach washing, and dry cleaning. Water is used for washing and rinsing during a typical decontamination process. The water used for decontamination must be collected and disposed of in a proper manner.

Workers in a variety of settings may be exposed to bio-hazardous substances which cause disease. Immunization may be recommended as one control measure to prevent illness if exposure cannot be avoided. Prior to the implementation of a workplace immunization program, a hazard assessment must be completed to determine the level of the workers’ risk of exposure.

For hazard control implementation, the employer should develop a plan which includes all methods of control to eliminate or prevent exposure including:

• Engineering controls, such as elimination, ventilation and structural arrangement of the workplace.

• Administrative controls, such as safe work practices or protocols, worker education and training. If these two primary methods cannot ensure control of exposure then personal protective equipment should be used.

• Personal protective equipment, which includes the use of gloves, gowns, respirators, etc. when working in areas where there is a risk of exposure.

Control water runoffWater runoff is controlled to maintain stability of excavations and trenches, and to prevent contaminated water from entering creeks, streams, or existing storm system. Pumping water is not always an option so other measures are put into place to help control the water runoff.

The easiest way to control water runoff is by establishing the grade of the job site. Grade tends to change as the work progresses because roads are built, excavations are dug, and the general



lay of the land changes. If the general lay grade of the site tends to slope in one direction, then ditches, silt fences, and ponds can be placed on the down slope to cut off the water before it runs off site. If the grade runs in more than one direction, then multiple ditches and measures should be put into place. If the existing grade conflicts with the work to be done, then multiple ditches need to be put into place to make the water migrate to a desired location.

With regards to excavations, Part 20 of the OH&S Regulations state:

20.95 Water accumulation(1) Water must not be allowed to accumulate in an excavation if it might affect the stability

of the excavation or might endanger workers.

(2) Erosion of slopes by surface water must be prevented if workers may be endangered.

Settling ponds are basins that control water pollution by catching contaminants from the water. They can be permanent or semi-permanent structures made from different materials. Settling ponds are used to treat water before releasing it into the environment. They are often dug out, lined with polyethylene, and then used for the duration of the job. Settling ponds are not usually filtered or emptied until work on the jobsite is completely finished.

Figure 9 — Settling pond



Rain and snow water can be contaminated by various construction activities which can travel into the environment if preventative measures are not in place. Contaminants can be anything such as sediment, oils and grease, heavy metals, debris, road salts, fertilizers, pesticides and herbicides.

Implementation of environmental protection has become crucial. Measures to prevent environmental contamination include:

Environmental fencingThe most common type of environmental fence for controlling and filtering water runoff is silt fence. Silt fence is a temporary sediment and erosion control measure.

Runoff pipes and storm systemsPipes and culverts can be used to channel water to desired areas and away from undesired areas. All water must be clean before letting it enter the storm system so filtration systems are a must before pumping into a live storm sewer.

Controlling damageEven with preventative measures in place, heavy rainfalls can cause unexpected water runoff. It is important that all down slopes have silt fences and/or cut-off ditches in place. Damage control must be swift, and should aim to rectify the current incident as well as to prevent future problems.

Ditches and trenches are sufficient to control water. Ditches force the runoff to desired areas. Ditches should be dug deep enough so that water does not run past them. Rock berms are often placed in ditches to filter dirty water and to slow the flow. Over time, these rock berms may need to be replaced as the silt builds up on the berms.

Figure 10 — Drainage ditch



Deeper trenches must be excavated in a technical manner. There are many standards that must be followed. Depending on the depth of the trench, the trench may need to be lined with plastic, or if the ground is porous then sheet pilings may need to be installed. It is important to note that the safety of workers is the top priority.

Earth berms require large amounts of soil and can be expensive to build. Guidelines vary based of the berm placement process, but the general process is as follows:

1. Mark out the berm location with survey paint or grade stakes

2. Flatten the area with a bobcat or excavator

3. Structural soil or clay should be brought in and place where the berm has been laid out. The height of the berm will vary based on the engineer’s specifications.

4. Shape the berm by hand and/or with the assistance of bobcats or excavators.

5. Compact the clay by hand or with the assistance of powered tampers.

6. Spread a layer of topsoil on top of the clay.

7. Rake out and shape the topsoil to suit the shape of the berm.

8. Plant turf, shrubs, or other plants over the berm.

Always follow the guidelines set out by engineer’s specifications and/or city authorities.

Protective berm

Toe of island

20.0 '

25EL. = + 6.0'

1

Figure 11 — Berm sloping

Temporary lighting and powerTemporary string lights are reliable, economical, and versatile lighting for a wide range of industrial applications. String lights eliminate much of the labour and potential hazards associated with wiring other types of temporary lighting. Their durability ensures that they can be reused on many work sites. Light plants provide an ideal solution for lighting sewers, tunnels, shipyards, aircraft and construction sites.



Figure 12 — Site lights

When using temporary lighting, do not attempt to setup, operate, or work on the light tower unless you have read and studied the manual and the engine and generator manuals carefully. Reading these manuals will teach you how to safely setup, operate, and properly maintain the tower and its components. Remember that you are the key to safety. Good safety practices not only protect you, but also those working around you.

Types of temporary lighting include:

• String lights

• Quartz lighting

• Light plants

• Tower lights

An employer must ensure that lighting at a work site is sufficient to enable work to be done safely. This includes ensuring that the light source be placed and protected above working or walking areas, and ensuring that emergency lighting be available at a work site if workers are in danger in the event that the normal lighting system fails. Emergency lighting must generate enough light so that workers can leave the work site safely, start the necessary shut-down emergency shut-down procedures, and restore normal lighting.

Never operate or set up a light plant unless you have read and studied the manual. All GFCIs should be in place and in proper working order. All sources for lighting should be placed on level ground and fully stabilized to ensure that is operates at optimal capacity. Only qualified personnel should inspect and maintain the lighting equipment.



Machinery should never be serviced or repaired unless the machinery has come to a complete stop, a proper energy-isolating device (grounding rod) has been activated, or the equipment has been otherwise rendered inoperative that can prevent accidental activation (lock-out procedures).

Figure 13 — Grounding rod

Site restorationSite restoration is performed when existing parcels or portions of the site are altered during construction and need to be returned to their original state once the work is completed.

The site restoration protocol will change from site to site but all engineer’s specifications, environmental acts, OH&S Regulations, and city authority directions and regulations must be followed.

Restoration activities may consist of replacing landscaping or previously removed material.

Documentation is used when having to restore conditions after construction has finished, most commonly from photos. Photos provide a clear guide for contractors and authorities to show what conditions looked like pre-construction, as they are not subjective and provide an accurate reference.



On any sizeable job there will be a landscaping plan for the landscaping and other components once the job is finished. Specifications will be stated for walkways, shrubs, and other growth in the plan. Sometimes these landscaping areas are in the same spots they were previous to construction but often times they move to another location.

Figure 14 — Restorative site plans

Tool crib attendant dutiesA tool crib attendant dispenses tools, equipment, supplies, and consumables to other workers. The attendant must be knowledgeable enough to identify the tools, visually inspect them for defects, identify the applications for each tool and what accessories go with the tools. Even though the worker requesting a tool should know what they need, it is still the responsibility of the crib attendant to supply them with the proper tool and accessories, in proper working order.

Inventory control includes two tasks: placing orders and receiving orders. It is important to keep a running list of the items you are getting low on and place orders when required. Do not wait until something runs out, especially Personal Protective Equipment. When receiving orders, check the transfer list. Make sure that goods that have been received have actually been transferred to the designated tool crib. Check that all barcodes correspond.

Signing tools in and out is the biggest part of the tool crib attendant’s job. Computer programs used for this vary from jobsite to jobsite and company to company. Get training on the program that is being used.



Whenever an item goes out or comes in, check it for leaks, damage, frayed cords, missing parts, excessive dirt, etc. Tag defective equipment and specify the problem on that tag. Check fluid levels before an item is issued, like a gas powered saw. Place a tag on the saw stating the fuel mixture. As a responsible tool crib attendant, be aware of provincial regulations and site safety rules. Never issue defective tools that may have the potential to cause an accident. Always err on the side of caution.

The trailer or tool crib must be kept clean, as well as the area where paperwork is done. Gloves should be worn when a tool comes in covered in an unidentified substance. Never use a solvent to clean an item. It is best to steam clean it if a steam cleaner or “jenny” is on hand. Remember that a rented tool returned dirty would cost the company a considerable cleaning fee.

Figure 15 — Tool crib

Always make sure that there is a secure lock on the tool crib and that it is free of tripping hazards. Keep the area outside the tool crib clear of snow, etc. Chain and lock up any outside tools as well as bottle carts and pipe stands.

Recycling materialsRecycling reduces the consumption of fresh raw materials and energy usage, and reduces the production of air pollution (from incineration) and water pollution (from landfilling). Materials that can be recycled are aluminum, asphalt, concrete, shingles, gypsum wallboard (drywall), steel, wood, plastic, carpet, lead, paint, ceiling tiles, glass, paper, formwork, and plywood.

Most construction recyclables need to be separated into proper bins or disposal areas as recycling centers will not take unsorted materials. Recyclable materials also go to different recycling plants. Designated areas are set up to be accessible for trucks to haul the materials off-site.



Some recycled materials (formwork, plywood) do not have to be sent away. They can be stored and reused on site. It is important to treat these materials with care in order to reuse them.

Figure 16 — Recycled materials


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British Columbia CONSTRUCTION CRAFT WORKER APPRENTICESHIP PROGRAM …€¦ · · 2017-07-06Competency E1: Prepare Site ... CONSTRUCTION CRAFT WORKER APPRENTICESHIP PROGRAM 7 COMPETENCy