Excavation safety

                                        Excavation safety

1.     Excavations:

Ø  There are about seven deaths each year due to work in excavations.

Ø  Many excavations collapse without any warning, resulting in death (or) serious injury.

Ø  The specific hazards associated with excavations are as follows:

ü  Collapse of the sides.

ü  Materials falling on workers in the excavation.

ü  Falls of people and/or vehicles into the excavation.

ü  Workers being struck by plant.

ü  Specialist equipment such as pneumatic drills.

ü  Hazardous substances, particularly near the site of current (or) former industrial processes.

ü  Influx of ground (or) surface water and entrapment in silt (or)mud.

ü  Proximity of stored materials, waste materials (or) plant.

ü  Proximity of adjacent building (or) structures and their stability.

ü  Contact with underground services.

ü  Access and egress to the excavation.

ü  Fumes, lack of oxygen and other health hazards (such as weil’s disease).

ü  Contaminated ground.

Precautions and controls required for excavations:

The following precautions and controls should be adopted:

v  At all stages of the excavation, a competent person must supervise the work and the workers must be given clear instructions on working safely in the excavation.

v  The sides of the excavation must be prevented from collapsing either by digging them at a safe angle (between 5º and 45º dependent on soil and dryness) (or) by shoring them up with timber, sheeting (or) a proprietary support system.

v  Falls of material into the workings can also be prevented by not storing spoil material near the top of the excavation.

v  The workers should wear hard hats.

v  If the excavation is more than 2m deep, a substantial barrier consisting of guard rails and toe boards should be provided around the surface of the workings.

v  Vehicles should be kept away as far as possible using warning signs and barriers.

v  Where a vehicle is tipping materials into the excavation, stop blocks should be placed behind its wheels.

v  The excavation site must be well lit and night.

v  All plant and equipment operators must be competent and non-operators should be kept away from moving plant.

v  PPE must be worn by operators of noisy plant.

v  Nearby structures and buildings may need to be shored up if the excavation may reduce their stability.

v  Scaffolding could also be stabilized by adjacent excavation trenches.

v  The influx of water can only be controlled by the use of pumps after the water has been channeled into sumps.

v  The risk of flooding can be reduced by the isolation of the mains water supply.

v  The presence of hazardous substances (or) health hazards should become apparent during the original survey work and when possible removed (or) suitable control measures adopted.

v  Any such hazards found after work has started, must be reported and noted on the inspection report and remedial measures taken.

v  Exhaust fumes can be dangerous and petrol (or) diesel plant should not be sited near the top of the excavation.

v  The presence of buried services is one of the biggest hazards and the position of such services must be ascertained using all available service location drawings before work commences.

v  As these will be probably not be accurate, service location equipment should be used by specifically trained people.

v  The area around the excavation should be checked for service boxes.

v  If possible the supply should be isolated.

v  Only hand tools should be used in the vicinity of underground services.

v  If the supply cannot be isolated then ‘goal posts’ beneath the overhead supply together with suitable signs must be used.

v  Safe access by ladders is essential, as are crossing points for pedestrians and vehicles.

v  Whenever possible, the workings should be completely covered outside working hours particularly if there is a possibility of children entering the site.

v  Finally care is needed during the filling in process.

v  Wells and disused mine shafts are found during construction work and must be treated with caution, and in the same way as an excavation.

Inspection and reporting requirements:

      The duty to impact and prepare a report only applies to excavations which need to be supported to prevent accidental fall of material.

      Only persons with a recongnized and relevant competence should carryout the inspection and write the report.

      Inspections should take place by a competent person at the following timing and frequency.

      After any event likely to affect the strength or) stability of the excavation.

      Before work at the start of every shift.

      After an accidental fall of any material.

      Although an inspection must be made at the start of every shift, only one report is required of such inspection every 7 days.

      However, reports must be completed following all other inspections.

      The report should be completed before the end of the relevant working period and a copy given to the manager responsible for the excavation within 24hours.

      The report must be kept at the inspection site until the work is completed and then retained 3 months at an office of the organization which carriedout the work.

      Almost all construction work involves some form of excavation (for foundations, drains, sewers etc) and every year people are killed (or) seriously injured while working excavations.

      Designers and those specifying the work should always consider the use of trenchless techniques, such as micro-tunneling, directional drilling and pipe bursting etc, which replace the need for excavation, apart from the launch and reception pits.

      They also reduce risks to members of the public from open excavations and subsequent traffic disruption.

      If excavations are required, the work must be properly planned and carriedout to prevent accidents.

      There is almost no ground that can be relied upon to stand unsupported in all circumstances and the risk in self-evident when you consider that it is quite common for one cubic metre of soil to collapse into an unsupported excavation, and this can weigh as much as one tonne.

      Before digging any trenches, pits, tunnels(or)other excavations, decide what temporary support will be required and plan the precautions that are going to be taken against:-

§  Collapse of the sides.

§  People and vehicles falling into the excavation.

§  Materials falling onto people working in the excavation.

§  Undermining nearby structures.

§  Underground and overhead services.

§  The inflow of ground and surface water.

Collapse of the sides (or) roof:

Ø  The need for adequate support will depend on the type of examination, the nature of the ground and the ground water conditions.

Ø  Install support without delay as the excavation progresses.

Ø  Any unsupported excavation will be safe without support only if its sides are battered back sufficiently (or) if the excavation is in sound rock.

Ø  Battering back the sides of an excavation to a safe angle is a simple and acceptable means of preventing instability.

Ø  In granular soils the angle of slope should be less than the natural angle of repose of the material being excavated.

Ø  A competent person who fully understands the dangers and necessary precautions should inspected excavation at the start of each shift.

Ø  Excavations should also be inspected after any event that may have affected their strength (or) stability (or) after a fall of rock (or) earth.

People and vehicles falling into excavations:

      Prevent people from falling by guarding excavations.

      Edges of excavations should be protected with substantial barriers where people are liable to fall into them.

      This can be achieved using guard rails and toe boards, which can be inserted into the ground immediately next to the supported excavation side (or) using fabricated guard rail assembles that connect onto the sides of the trench box.

      All excavations in public places should be suitably fenced off to prevent members of the public approaching them.

      Prevent vehicles from falling into excavations by keeping them out of the area.

      Vehicles passing close to the edges of excavations may also overload the sides leading to collapse.

      Where necessary use baulks (or) barriers to keep vehicles away from excavated edges.

      Where vehicles have to tip materials into excavations, prevent them from overrunning into the excavation by using properly secured stop-blocks.

      These must be placed at a sufficient distance from the edge of the excavation to avoid the danger of the edge breaking away under the weight of the vehicle.

      The sides of the excavation may also require extra support.

Materials falling into excavations:

      Do not park plant and vehicles (or) store excavated spoil and other materials close to the sides of excavations.

      The extra lodgings from spoil, vehicles etc can make the sides of excavations more likely to collapse.

      Loose materials may fall from spoil heaps into the excavation.

Undermining nearby structures:

      Make sure excavations do not undermine the scaffold footings, buried services (or) the foundations of nearby buildings (or) walls.

Underground and overhead services:

      Many serious accidents have occurred when buried services have been damaged during excavation work.

      Excavation work should not start until steps have been taken to identify and prevent any risk of injury arising from underground services.

      Burns and electrocution can result if raised tipper truck bodies (or) excavators touch (or) come close enough to overhead power lines to cause arcing.

      The need to undertake excavation work close to (or) below such lines should be very carefully considered and avoided where possible.

Ground and surface water in flow:

      Depending on the permeability of the ground, water may flow into any excavation below the natural ground water level.

      The supports to the side of the excavation should be designed to control the entry of ground water and the design should take any additional water loading into account.

      Water entering the excavation needs to be channeled to sumps from where it can be pumped out; however the effect of pumping from sumps on the stability of the excavation should be considered.

Excavation checklist:

      Is there adequate support for the excavation (or) has been it sloped (or) battered back to a safe angle?

      Is there a safe method used for putting in the support, without people working in an unsupported trench?

      Is there safe access into the excavation eg. A sufficiently long, secured ladder?

      Are there barriers (or) other protection to stop people and vehicles falling in?

      Are properly secured stop blocks provided to prevent tipping vehicles falling in?

      Could the excavation affect the stability of neighbouring structures (or) services?

      The materials, spoil and plant stored away from the edge of the excavation to reduce the chance of a collapse?

      Is the excavation regularly inspected by a competent person?

Other aspects of excavation safety:

      Provide a safe means of getting into and out of an excavation.

      If a risk assessment identifies that ladders are a reasonable means of access and egress from an excavation, they must be suitable and of sufficient strength for the purpose.

      Donot use petrol (or) diesel engines in excavations without making arrangements for the fumes to be ducted safely away (or) providing for forced ventilation.

      Do not site petrol (or) diesel engined equipment (such as generators (or) compressors) in (or) near the edge of an excavation.

Inspection and reports:

      Excavations that need to be supported (or) battered back to prevent danger must be inspected.

      The person in control of the examination must arrange for a competent person to carryout these inspections:-

Ø  At the start of the shift before work begins.

Ø  After any event likely to have affected its stability.

Ø  After any accidential fall of rock, earth (or) other  material.

Ø  If the competent person is not satisfied that work can be carriedout safely, they should advise the person the inspection was carriedout for as soon as possible and the excavation should not be used until the defects have been put right.

Ø  A written report should be made following most inspections.The competent person must:

ü  Complete the inspection report before the end of the working period; and

ü  Within 24 hours provide a copy of the report to the person for whom the inspection was carriedout.

Ø  The person receiving the repot must:

ü  Keep it at the site where the inspection was carriedout until construction work is completed;and

ü  Thereafter keep it at an office for three months.

Ø  For an excavation only one written report is required within any seven-day period, unless there has been a collapse/fall of material (ot) other event likely to affect stability.

Ø  In this case an inspection and report are required before work starts again.

Ø  The report should contain the following information:-

ü  Name and address of the person the inspection was carriedout for.

ü  Location of the place of work (or) work equipment inspected.

ü  Description of the place of work (or) work equipment inspected.

ü  Date and time of the inspection.

ü  Details of any matter identified that could give rise to a risk to the health (or) safety of any person.

ü  Details of any action taken as a result of any matter identified in the point above.

ü  Details of any further action considered necessary.

ü  Name and position of the person making the report.

Underground services:

      Many serious accidents have occurred when buried services have been damaged during excavation work.

      Every effort should be made to excavate along side the service rather than directly above it.

      Mechanical excavators should not be used within 0.5m of the indicated line of a service.

Excavate using safe digging practices:

      Hand dig near buried pipes (or) cables (or) use air-powered excavation devices.

      Donot use an excavator to excavate within 0.5m of a gas pipe.

      The flow diagram will help you undertstand the process, from referring to plans on site through to the start of the excavation.

Services located and confirmed by trial holes as necessary?

Use locating devices

Refer to plans of buried services

Excavation planned

                                                     

Is there a reasonable explanation for not being located?

 

                                                                                                                                                No                                          No

Contact owners of services

Services exposed

Evidence of other services

                                                                                                                  Yes

Obtain more information and plans if possible

                                               Yes                                                        Yes                   No    

        

Use tools of choice

Is work close to the services?

                No

Carryout excavation near services by hand digging

                                                     Yes                                                  No

Three types of excavation work:

      Trenches, basements, wide excavation and shafts.

Trenches:

      Major causes are materials falling into the trench striking those below and also both plant and people falling into the excavation.

      A hydraulic excavator should never be used to clear away the debris for fear of causing further serious injury to the buried person.

      Previously excavated ground is the cause of which collapse.

      Similarly, slipping and collapse may occur in rock excavations when beeding planes dip staply across the line of the excavation.

      The use of explosives in the excavation process may well trigger off a slipping movement.

      Excavated spoil, pipes, bricks and timbering equipment stored too close to the edge of a trench may produce a surcharge load which is too great for the trench sides to withstand.

      Excavation is rarely homogenous ground.

      Previously excavated ground reduces the inherent strength of the adjacent ground.

      When previously excavated ground is close to (or) crosses the new trench collapse may well occur.

Examples:

      when pipes cross a newly excavated trench the ground in the vicinity of a previous excavation will be very weak and particularly suspectible to failure.

      If a previously excavated trench exists approximately parallel to and within a meter of the new trench, the ground between them will be weak and very likely to collapse.

      A further example, not exactly of a previous excavation, is of that where bushes (or) trees are in close proximity to the line of the new trench whether (or) not they have been grabbed up before excavation starts.

      When a trench is excavated close to and to a depth to (or) below the foundations of a building (or) structure the surcharge load may not only cause the collapse of the sides of the trench but also may cause the collapse (or) partial collapse of the structure.

      Many fatal and serious accidents have occurred in unsupported trenches which have only been open for an hour (or) to a substantial proportion have occurred during the day of the excavation.

      The ways to prevent collapse and make working in excavations safe are either by:

Ø  Timbering (or) shoring. i.e supporting the sides(the proportion of physical support for each side of the trench).

Ø  Battering the sides to a safe angle.

      Battering requires the sides of the excavation to be sloped more than the angle of repose for the soil.

      A guide to the safe angle at which homogenous soils will stand is given in timber in excavation.

      As excavation proceeds the exposed sides are supported by timbering (or) trench sheets laid horizontally behind the flanges of adjacent piles and wedged in position against the ground.

      As trench bottom work proceeds, the boxes are pulled along, usually by the excavator, and the men remain inside within the protection of the side sheeting.

      In Britain the CHSW regulations require that any excavation must be inspected by a competent person:

Ø  After any event likely to have affected the strength (or) stability of the excavation (or) any part thereof.

Ø  Workers being struck by excavating machinery are the hazard of trench work.

      The rocks may be loosened first during the excavation process and subsequently by vibration (or) from being struck when materials are lowered into the trench.

      To prevent workers being struck by excavating machinery a safe method of working needs to be implemented.

      During the excavation cycle no person should be allowed in the vicinity of the machine.

      When the excavator driver cannot see all parts of the jib and bucket during the excavation cycle (or) when the machine is used as crane to lower materials(eg.pipes) into the trench, an experienced bankman should be used to guide the driver and to ensure that people remain well clear of the operations being undertaken.

      Measures to prevent vehicles falling into excavations are required under the CHSW regulations.

Basement and wide excavations:

      Most of the hazards of trench work are also applicable to wide excavations.

      However, supporting the sides of a deep and wide excavation may be safely carriedout by the following methods.

      Before excavation a diaphragm wall is sometimes formed around the perimeter of the site.

      This is designed to act as a retaining wall for the sides of the excavated basement.

      Following the construction of the wall excavation may then take place to the necessary reduced levels in perfect safety for the operatives, since the sides are presented from collapsing timber runners (or) trench sheets are installed progressively in a narrow excavation around the edges of the site.

      The runners are used in conjuction with walings at suitable vertical centres and the ground pressures transformed via the walings through a system of raking shores and thrust blocks at their lower ends, to the unexcavated ground.

      When the close boarding has been installed the rest of the excavation can be carriedout in safety.

      When construction basements, deep excavations and shafts, it is particularly important to construct a solid fence around the site before excavation is started.

Shafts:

      With shaft construction the hazards are similar to those for trenches i.e materials falling into the shaft from ground level, earth (or) boulders falling from the sides and people falling into the excavations.

      Support of the sides during shaft construction may be carriedout with traditional timbering installed progressively with the shaft excavation.

      At the top, the timbering should be extended to form a fence so that people and materials are prevented from falling into the excavation.

      Shafts of larger diameter may be constructed with precast concrete lining rings installed as excavation proceeds, thus providing constant supporting to the sides.

      Where excavation is to proceed at a faster rate than lining installation some form of temporary support for the sides must be used.

Deep bored piles:

      For inspection purposes, for bottom preparation such as cleaning out and sometimes for hand digging extensions to under-reams, deep bored pile excavations must be entered.

      No descent is to be allowed into an unlined borehole more than 12hours after the start of excavation (or) more than 3 hours after completion-these periods may need to be shortened.

      After the erection of the temporary huts and offices etc. on any building site, large (or) small, foundations must be prepared.

      Experience shows that when accidents occur in excavations they are usually extremely serious.

      Therefore, when excavating it is necessary to understand that the construction(general provisions) regulations 1961 apply, and both employers and employees have certain duties and obligations to fulfil.

      It is essential to ensure the safety of work people who may be working in (or) around the excavations, and protection for employees of other firms working on the same site.

      There are many misconceptions in regard to safety of excavations, and it should be known that there is hardly any type of ground whatsoever which, given the right set of circumstances, may not collapse.

      It is necessary to prevent this, either by battering the edge of  an excavation so that the ground slopes to its natural angle of repose, (or) to supply and use suitable materials to stop the sides from sliding in.

      Besides making sure that excavations donot fall to people who may be working in them, there is a need to ensure that people, and materials, do not fall in from the top.

      Ropes and spigots are considered adequate provided they are far enough away from the edge to warn people effectively that there is an excavation, also, that the spigots are not driven into the ground in such away to cause damage (or) weaken the side of the excavations.

      The construction of high rise buildings are exposed to the hazards of various natures, from excavation below ground level.

      Before excavation work is carriedout, the relevant person (or) principal contractor, for construction work must:

Ø  Find out what underground services exist,

Ø  Obtain relevant information about the service(location, type, depth, restriction to be followed).

Ø  Record the information.

      A relevant person is responsible for managing the risks associated with:

Ø  An excavation collapsing.

Ø  Objects falling into an excavation.

Ø  A person falling into an excavation.

Ø  Substance exposure in an excavation, for example, carbonmonoxide from plant.

      A barricade (or) hoarding at least 900mm must be erected around an excavation unless it is not possible (or) no members of the public are likely to be in the area of excavation.

      1926 Subpart P. Excavation 1926.651 Specific Excavation Requirements.

      A barricade atleast 900mm high must be erected around a trench that is 1 metre (or) more deep unless it is not possible (or) only workers involved with the trench will be in the area (or) another form of barrier exists, for example, excavated materials near the trench.

Excavation hazard:

      Fall of person

      Fall of material

      Sand sliding

      Slip, trip, fall

      Flooding

      Underground electrical cables

      Dust inhalation

      Underground pipelines

      Body parts injury

The major hazard and risk activity in excavation.

      Excavation hazards are addressed in specific standards for the construction industry.

      This section highlights OSHA standards, the regulatory agenda, directives and standard interpretations related to excavation.

      Excavation is regarded as one of the most hazardous construction operations.

      Excavation failure occurs very quickly, giving a worker virtually no time to escape, especially if the collapse is extensive and the excavation is a trench.

      Normally, a slab of earth collapses off the trench face under its own weight and breaks against the opposite wall of the excavation burying and crushing any person in its path.

Planning the work:

v  Before starting an excavations, it is important to plan the work by following a comprehensive planning procedure so that all significant hazards can be addressed.

v  The most immediate ones for planning purposes are the following:

Ø  Control of people and vehicles around the surface area of the excavation.

Ø  Storage and disposal of excavated material.

Ø  The most suitable method of temporary support of the excavation walls.

Excavation work hazards on site:

ü  Excavation work is one of the most hazardous operations of the construction process.

ü  Occupational hazards associated with excavation work are numerous and range from collapse of excavation sides to the possibility to get such a disease as tetanus.

ü  The key to safety in excavation work in proper planning, supervision, management and carrying out.

ü  The most immediate hazards of excavation work are collapse of sides, falling materials from sides of excavation;falls of people and machinery into the excavation and undermining of structures in the proximity of excavation as well as access and egress to the excavation.

ü  Member of the public must be also protected from the hazards posed by excavation work.

ü  The main hazards associated with excavation work are  as follows:

Ø  Materials falling on workers in the excavation.

Ø  Dangers associated with excavation machinery.

Ø  Falls of people and/or vehicles into the excavation.

Ø  Access and egress to the excavation.

Falling materials:

      Spoil heaps should be kept a meterback from excavation edges and vehicles such as trucks and dampers should be kept well away from edges.

      Within an excavation should wear safety helmets.

Falls into the excavation:

      Solid guardrails should protect the edges of excavation more than 2meters deep, and anywhere the public can approach should be fenced off regardless of depth.

      Traffic routes should keep vehicles away from excavators to present our loading pressures to the soil in the area.

      Work should be planned to ensure that excavations are either securely fenced, covered (or) backfilled during working hours, overnight and at weekends.

Summary of precautions and controls:

      Excavation must be constructed so that they are safe environments in which construction work can take place.

      The first form of control is to decide whether the excavation is necessary.

      These have been many technological advances which have eliminated the need for excavation work.

      Excavation work is the only option available, the following precautions and controls should be adopted:

Ø  at all stages of the excavation, a competent person must supervise the work.

Ø  Workers must be given clear instructions on working safely in the excavation.

Ø  The walls of the excavation trench must be prevented from collapsing either by digging them at a safe angle (or) by shoring them up with timber, sheeting (or) a proprietary support system.

Ø  Falls of material into the workings can also be prevented by not storing spoil material near the top of the excavation.

Ø  If the excavation is more than 2m deep, a substantial barrier, consisting of guard rails and toe boards should be provided around the surface of the workings.

Ø  Workers should never enter and unsupported excavations (or) work ahead of supports.

Ø  Where a vehicle is tipping materials into the excavations, stop blocks should be placed behind its wheels.

Ø  Whenever it is possible, workers and moving plant, such as excavations, should be kept separated.

Ø  Nearby structure and buildings may need to be shored up if the excavation may reduce their stability.

Ø  Scaffolding could also be stabilized by adjacent excavation trenches.

Ø  Exhaust fumes can be dangerous and petrol (or) diesel plant not be sited near the top of the excavation.

Hazard identification:

      Collapse of the sides.

      Falls of people and/or vehicles into the excavation (stop blocks for dampers).

      There is no access and egress to the excavation(Access and egress must be provided to the excavation.eg.step type or ladder).

ü  A trench is a type of excavation in the ground.

ü  Excavation work is high risk.

ü  Before undertaking any excavation it is essential that appropriately skilled and qualified personnel have been consulted to ensure all hazards have been identified and appropriate controls have been put in peace.

Hazard:

      Earth (or) rock around the hole collapses structures an excavation site can become unstable.

      Contaminants can be uncovered during excavation.

      Unexpected water flows can occur when excavation work digs below the water table (or) the level which the water table rises to after rain.

      Fall (or) collapse of material (or) plant into the excavations.

      People falling into excavated area.

Hazard	Threat	Consequences	Control
Underground services, cables, oil, gasoline water/irrigation pipe	Cable cut rupture of pipe. Uncertainity of cable location	Electrocution loss of services loss of containment	Permit of work system excavation certificate. Trail pit
Presence of hydrocarbon gas/vapour H2S gas, carbonmonoxide	Excessive exposure inhalation exhaust of internal combustion engines kept too close to excavation	Asphyxiation respiratory problem poisoning fire/explosion	Gas test, PPE Make aware of dangers keep vehicle exhausts away from excavation toolbox talk.
Insufficient oxygen	Gases fumes displacing oxygen in excavation	Asphyxiation	Gas test
Use of plant and machinery JCB/Dumper	Untrained operator the driver unable to see the digging area defective plant	Accident cable cut	Authorized competent Regular inspection of plant
Excavation confined space	Excavated materials stored too close to edge person unaware of existence of excavation	Excavation caving in injury person falling in the excavation	Store material 1 meter away barricade excavation and use warning signs. use warning lights at night.
Large quantity of water entering excavation	Heavy rain water table at shallow depth/excavation near water sources Inadequate emergency   access out of excavation Congested work site Personnel working at edge/above excavation	Excavation caving in Fatality/injury Injury to self (or) others Drop of tool/equipment on to people working in excavation	No work should be carried out during rain and work to be started after ascertaining water table water sources nearby Excavation shall have adequate access No.of personnel working in excavation to be limited Tools/equipment to be kept away from edge of excavation. Tool box talk
Heat stress	Personnel working in hot environment	Heat sickness/stroke	Adequate water shade and rest to be provided

Failure of excavation:

      Planes of weakness in soil.

      Saturation of soil by rain (or) water leaks.

      Construction at too steep an angle.

      Over loading the top.

      Earthquakes and vibration.

Safety measures:

v  Trench excavation should not harm

ü  The workers

ü  The public

ü  Adjacent existing structures

v  Cracking back of the top of the slope back to a distance equal to the height of the slope, bulging at the centre of the toe of the slope and soil particles running off the slope below the excavation machinery are important danger signals which must be watched by the construction supervisor.

v  The following points need special attention:-

Ø  The edge of the excavation should be kept clean of all material

Ø  Heavy equipment and road traffic should be kept away from the excavated sides at a distance not less than the depth of the trench (or) atleast 6m for trench deeper.

Ø  Depth of water table near the excavation should be ascertained, the location of any near by water source should be looked for the excavation should be examined for entry of water.

v  The objective is to provide practical guidance for administrative, technical and educational frame work for safety health in excavation with a view to:-

Ø  Prevent accidents and diseases and harmful effects on the health of workers arising from employment in excavation.

Ø  Ensuring appropriate design and implementation of excavation project.

Ø  Providing means of analyzing from the point of view of today, health and working conditions, excavation process, activity, technology and operation and taking appropriate measure of planning, control and enforcement.

v  Trench excavations are those where the horizontal width of ground level is less than the vertical depth of the deeper side.

v  Open excavations are wider than trenches and include foundations, building sites and the like.

Legal requirements:

      All work involving excavation must comply with the requirements in the HSE Act and the HSE regulations.

      The provision of the HSE Act and regulations and the building act and regulations, which generally apply to excavation and appendix to this code.

Modes of failure:

      It should be noted that all excavations, no matter what depth, may be hazardous.

      Modes of failure will depend on the depth, the soil type (or) soil types if layered, bedding planes, vibration, the presence of moisture, rain, (or) a high water table level, any super imposed loading close to the edge of the excavation the time the excavation in open, and any previous disturbance of the soil.

      Removal of soil from an excavation causes unbalanced soil stresses.

      The use of a shoring system, (or) the cutting of the sides of the excavation to a safe slope, will help compensate these soil stresses.

General requirements:

      The following requirements apply to all excavation in which employees are required to work.

      Excavation to be shored

ü  Excavation shall over than 1.5metres have been known to collapse.

ü  Employees are to consider such excavations and determine if special precautions (or) work methods are necessary

ü  Excavation 1,5m (or) deeper

ü  Excavation greater than (or) equal to 1.5m deep are particularly hazardous and must be shored unless.

Safe slope in excavations:

v  Unless the stability of the excavated face is determined by a registered engineer (or) a competent person (experienced in excavations), the safe slope should not exceed:-

ü  1V:1.5H (or) the angle of repose, whichover is flatter for saturated (or) submerged soild (or) for excavations greater than 3min depth.

ü  Where the slope of an excavation is bached, the maximum height between benches should not exceed 1.5m, excepting the bench adjacent to the work area, which should not exceed 1m.

ü  Overall the total width of the benched excavation should not be less than required.

Shoring:

      On large and extensive excavations, the shoring should be designed by a registered engineer.

      The shoring of a face must be carried along with the excavation with the least possible delay between the excavation of the face and the completion of the shoring.

Materials and loads above excavations:

      Excavated (or) other loose materials must be effectively stored (or) retained not closer than 600mm from the edge of the face unless the face is specially shored to allow for the increased load, and suitable load, and suitable toe boards (or) other safeguards are provided.

      600mm from the edge of an excavation which is battered to a safe slope.

Excavations adjacent to buildings (or) structures:

      Where it is intended to excavate along side another structure, the following precautions must be observed.

      Never excavate below the level of foundation of any adjacent structure (or) within an area which should be inside the safe slope unless adequate precautions have been taken to ensure that the stability of the excavation face and the building (or) structures above are not at risk either during (or) after excavating.

      If an excavation is likely to affect the stability of existing structures, advice from a registered engineers must be obtained before the excavation is started.

Fencing:

      Excavation carriedout at any place to which the public have (or) might gain access must be guarded to avoid danger to people.

      Safety devices must be properly maintained until the excavation is completed (or) when there is no longer any deeper.

      Where during construction, an excavation is likely to collect (or) retain water of such a depth as will constitute a hazard to children (or) persons in the vicinity, the excavation must be covered (or) fenced off during times when employees are not present.

Protection from falling objects:

      Where excavation work is in (or) near public access ways and hazards exist, barricades, overhead protection, enclosed walkways (or) other means of protection must be provided for the public.

Protective helmets, googles, hearing protection:

      Hard hats must be worn both in the excavation and out of the excavation.

      Wind blow grit and dust are the most common sources of eye damage in excavation work.

Examination of excavation;

      Excavations including shoring and underpinning, must be examined by the employer (or) the employer’s representative before work starts each day, after rain (or) any occurrence that could affect the stability of an excavated face.

Other safety precautions:

Surface water and drainage:

      In all excavations, the safety of faces and fillings often depends on the effectiveness of the control of surface and ground water.

      Any inflow should be collected in sumps and pumped clean of the excavation.

      Springs coming up through the floor of an excavation are another cause of unstable conditions.

Harmful gases:

      Employees must be protected against the effects of toxic (or) explosive gases which may be encountered when carrying out work in trenches, open excavations by wearing approved equipment in relation to the type of hazard encountered.

      Excavations being below ground are a natural receptacle for all gases heavier than air.

      One of the more commonly used and effective methods of prevention is to use special ventilation equipment to blow clean air into the excavation in sufficient quantities to dissipate the foul air,

      The gases (or) fumes most likely to found in various kinds of excavations are set out.

Gases commonly found in excavations and trenches:

      Type of ground-Gases (or) fumes found

      Peaty ground-Methane, hydrogen sulphide

      Filled and made ground-Carbondioxide, hydrogen sulphide

      Reclaimed land and tip fills-carbondioxide, methane

      City streets-natural gas, carbondioxide, steam

      Thermal areas-Carbonmonoxide, carbondioxide, hydrogen sulphide, sulphurdioxide, methane

      Petroleum installations, service stations-petrol fumes, LPG, kerosene

Underground services:

      Because of the many services such as electric power cables, telegraph cables, gas pipes, water, oil pipes and sewer reticulation that are located underground, employers must, before starting work, as certain the location of all services that are likely to be affected by the excavation.

      When the existing services are uncovered during excavation, proper supports must be provided and all practicable steps must taken to prevent danger to employees (or) unnecessary interruption to these services.

Blasting:

      Where blasting is to be carriedout, in connection with excavation work, a certificated construction blaster must be incharge of the actual blasting work.

Recommended safe practices for excavators:

Before excavation:

General:

      Excavation work involves the removal of rock, weathered rock, gravels and/or soil.

      The sides of any excavation have to potential to collapse.

      Excavation work should therefore be carefully planned.

Planning:

      What is the best method of excavation?

      What is the best type of support for the sides of the excavation (or) can the sides be cut back to a safe batter?

      What is the best method, if occasion demands, of keeping water out of the excavation and reasonably dry, so that work can proceed without interruption?

Investigation:

      The effect of excavation may have on adjoining occupiers, adjacent structures, roading and underground services such as electricity, gas (or) water recirculation, and on the safety of persons in the vicinity.

      The nature of the soil to be excavated and its method of disposal, the length and nature of the haul route, the conditions of tipping (or) spreading.

During excavation:

Access for employees:

      The floor of the excavation must be kept clean of loose spoil, debris, tools, timber (or) anything that would impede employees safe egress in an emergency.

      Where an excavation, trench is of such small dimensions that it is not practicable to use ladders as a means of access (or) egress, other means must be provided to allow employees safe access and egress.

      Ladders used in an excavation must be constructed of suitable materials, conform to the appropriate newzealand standard, and be maintained in good order (or) condition.

      In deep excavations, temporary stairways should be used as they provide a safer means of access than ladders.

Separation of traffic:

      Excavation is so shallow that those outside can see and talk readily to those at the face, an efficient signaling system and interlocks that prevent the operation of winding gear, while personnel are moving, must be provided.

      Where mechanical haulage is used in small drives (or) manholes, refuges should be excavated into the side of the drive to provide shelter from passing traffic.

Adequate lighting:

      Trenches and open excavations where there is insufficient natural lighting should be provided with adequate artificial lighting.

Handling large diameter pipes:

      Before of the dangers involved in handling and positioning heavy pipes in and about excavations, the following general safety guidelines should be observed:-

Backfilling and compacting:

      Particular care needs to be taken while backfilling and compacting trenches.

      The vibration from the compactors can loosen soil from the trench sides and cause collapse.

      In addition the fumes from the exhaust can fill the excavation.

Trenches with battered sides;

      Trench sides which are battered to stable slopes should not exceed the safe slope limits.

      Where shoring is used as a means of supporting trench walls, the sizes of struts walings and sheeting material must not be less than the minimum sizes prescribed.

      Where the trench is in saturated used must be such as to prevent the movement of fine material out of the bank.

Shields (or) boxes and proprietary systems:

      Shields are frequently used in wide excavations for the installation of large diameter pipes where greater disturbance of ground occurs.

      Whilst they do not in effect provide support to the trench walls, they are a very effective means of preventing the collapse of ground on employees within the excavation.

Trenching: safety checklist

      Is the surface clean of plant, spoil heaps materials etc. for at least 600mm from the edge of the excavation?

      Is the trench clear of employees while the special heap is being worked on?

      Is the space between the trench and the spoil heap clean of pipes, bricks, stones, tools etc?

      Are the employees who are excavating and shoring the trench experienced in this sort of work?

      Have correct pins been used in steel trench struts?

      Is the method of with drawing sheeting and support for the trench during back fill safe?

      Is visibility adequate in trench?

Open excavations:

General:

      Open excavations vary in plan from an extra wide trench in open ground to and irregular shape defined by adjacent buildings as in city centre developments.

      It is difficult to provide standard solutions for the support of these wide excavations as so many site factors have to be taken into account.

      It is therefore recommended that open excavations are designed by suitability qualified and experienced persons.

      The hazards to employees in open excavations are not quite so immediate as i confined trench work.

      However it necessary to safeguard against failures of excavated faces to prevent loss of life and property.

Protection and support system:

      Where space is available, the sides of the excavation should be battered to a point where they become stable and donot exceed the safe slope requirements prescribed.

      For a given depth, a wide excavation when supported by walings and struts will require heavier struts to the frames than a trench supported in a similar manner.

      For very wide excavations, ground anchors, tie rods (or) rating struts should be considered.

Descent into confined spaces:

      Wherever practicable, a descent should not be made into an unlined shaft more than 12 hours after completion of excavation.

      Where entry into the shaft is necessary more than 12 hours after excavation, it must be reexamined by a competent person before any further descent takes place.

      Wherever practicable, hand excavation work should be limited to the clearance of loose spoil, softened zones in the base and limited excavation within the time limit.

      Excavated (or) other loose material must be effectively stored.

      Excavations carriedout at any place to which the public have (or) might gain access must be guarded to avoid danger to people.

      An excavation is likely to collect (or) retain water of such a depth as will constitute a hazard to children.

      Employers must be protected against the effects of toxic (or) explosive gases which may be encountered when carrying out work in trenches, open excavations by wearing approved equipment in relation to the type of hazard encountered.

2.Foundations:

Hazard:

      Fall of person

      Fall of material

      Sand sliding

      Dust inhalation

      Hit by objects

      Body parts injury

      Collapse of adjacent structures

3.Demolition:

      Demolition are high-risk activities whose safe execution is complex and technical and where expertise is vital.

      They require careful planning and execution by contractors who are competent in the full range of demolition techniques.

      During demolition, workers are injured in falls from edges through openings and fragile surfaces.

      Dust, noise and vibration are also significant problems that need to be considered and controlled when planning any demolition work.

      The CDM regulations apply to all demolition.

      A systematic approach to the demolition process starts with responsible clients who have a legal obligation to appoint adequately resourced and competent duty holders such as structural engineers, planning supervisors and principal contractors.

      It is vital that clients also fulfill their legal obligation to provide information about the structure to be demolished and this often means commissioning a pre-demolition structural survey from a structural engineer.

      It is good practice to consult a structural engineer at the planning stage of demolition to avoid uncontrolled collapse.

      The principal contractor, who may also be the demolition contractor, must be able to co-ordinate and manage the health and safety issues during the demolition works.

      References must be sought and pertinent questions asked by the client to establish the credibility of the demolition contractor, especially if its intended to appoint the demolition contractor as the principal contractor for the demolition phase of work.

v  Demolition is one of the most hazardous construction operations and is responsible for more deaths and major injuries than any other activity.

v  The principal hazards associated with demolition work are:-

      Falls from height (or) on the same level

      Falling debris

      Premature collapse of the structure being demolished

      Dust and fumes

      The problems arising from split fuel oils

      Manual handling

      Presence of asbestos and other hazardous substances

      Noise and vibration from heavy plant and equipment

      Electric shock

      Fires and explosions from the use of flammable and explosive substances

      Smoke from burning waste timber

      Pneumatic drills and power tools

      The existence of services, such as electricity, gas and water

      Collision with heavy plant

      Plant and vehicles overturning

v  Before any work is started, a full site investigation should be made by a competent person to determine the hazards and associated risks which may affect the demolition workers and members of the public who may pass close to the demolition site.

v  The investigation should cover the following topics:

      Construction details of the structures (or) buildings to be demolished and those of neighbouring structures (or) buildings.

v  A risk assessment should be made by the project designer who will also plan the demolition work.

v  A further risk assessment should then made by the contractor undertaking the demolition.

v  A written method statement should be produced before demolition takes place.

v  The contents of the method statement should include the following:-

      Details of method of demolition to be used, including the means of preventing premature collapse (or) the collapse of adjacent buildings and the safe removal of debris from upper levels.

ü  There are two forms of demolition:

v  Piece meal-Where the demolition is done using hand and mechanical tools such as pneumatic drills and demolition balls.

v  Deliberate controlled collapse-Where explosives are used to demolish the structure. This technique should be used only by trained, specialist competent persons.

§  A very important element of demolition in the training required by all construction workers involved in the work.

§  Specialist training courses are available throughout the world for those concerned with the management of the process, from the initial survey to the final demolition.

§  However, induction training, which outlines the hazards and the  required control measures, should be given to all workers before the start of the demolition work.

§  Demolition is one of the high risk activities of the construction industry with a fatal and major injury accident incidence rate about 17times that for the whole of the construction industry.

§  Approximately 10% of all fatal accidents each year in the construction field occur in the demolition sector.

§  Detailed guidance on acceptable standards and procedures in demolition is contained in BS 6187:1982

§  Code of practice for demolition and in HSE guidance note GS29 health and safety in demolition work.

§  Demolition is a very skilled process and to be carried out safely and correctly requires a great deal of knowledge of building construction and expertise in demolition methods.

Key to safe demolition:

      For any demolition operation to be undertaken safely and efficiently, not only is a careful preliminary investigation of the structure necessary but also the results of each step in the demolition process must be accurately forecast.

      It is important to identify the whereabouts of gas, electrical and water services and to ensure that they are disconnected (or) isolated before demolition works starts.

Demolition method:

      The pre-survey should identify the problem areas and provide all the information necessary to determine the method of demolition to be used.

      Moreover, as already indicated, it is any important to forecast the result of each step in the demolition process and thus to determine the precautions necessary to prevent premature collapse causing injury to personnel.

      The arrangements should include the provision of protective fans (or) nets and hoardings (or) another provision for preventing public access to the building being demolished.

      Identify responsibilities of the person in charge of operations and the responsibilities and duties of people to whom control of certain aspects of the demolition work will be delegated.

      Obviously not everyone engaged in demolition work will understand the structural significance of the various component parts he has to demolish and therefore demolition workers will need close supervision and guidance from some one skilled in the work if they are to proceed in safety.

      It is important that supervisors have a considerable knowledge of building construction as well as demolition methods.

      The CHSW regulations require that anyone planning (or) carrying out demolition work must be under the supervision of a competent person.

      A restricted zone for all people should be maintained around the structure to be demolished.

      When the demolition method is by pulling by wire ropes, the restricted zone should be three quarters of the distance between the winch and the structure to be demolished on either side of the rope and forward of the winch (or tracked vehicle) used for pulling.

Methods of demolition:

      The danger in demolition work varies with the method employed, which itself has a bearing on the number of workers at risk and their working time at heights and in around the structure being demolished.

      Methods of demolition many conveniently be divided into three categories, hand, mechanical and explosive.

Demolition by hand:

      Demolition by hand is progressive demolition, carriedout piecemeal with hand tools such as sledge hammers, jack hammers, concrete breakers and cranes for lifting and lowering purposes.

      It is carriedout in reverse order to the construction process, i.e  the roof covering is taken off first, followed by the roof trusses and upper ceiling and the building in the demolished storey by storey.

      Standing on the wall being demolished is unnecessary and should not be permitted.

      Similarly, any holes in floors in the building under demolition should be protected by guardrails and toe boards to prevent people falling.

      Structural collapse has occurred where floors have been overloaded by the accumulation of debris from parts of the building already demolished.

      Where scaffolding is used to provide a working platform care is needed to ensure that sufficient ties are provided at the lower levels before demolition (and hence removal of tiles) at the higher levels.

Mechanical methods of demolition:

      Include the use of a demolition ball (or) pusher arm, inducing deliberate collapse: and pulling by wire rope.

      Sometimes it is necessary to demolish by hand until the structure has been reduced to a height convenient for one of the mechanical techniques to be used.

For demolition by demolition ball:

      A swinging weight is used suspended from a lifting appliance, to demolish the structure progressively.

For demolition by pusher arm:

      A steel attachment is used, fixed to an extended jib arm on mechanically operated mobile plant.

      It exerts a horizontal thrust similar in technique to a battering ram and is used to demolish walls.

      The application of the pusher arm to the wall being demolished should never be more than 600mm below the top of the wall.

      In the demolition method of deliberately induced collapse key structural members are removed, causing, the whole (or) part of the building to collapse.

      Where partial demolition of a structure is to be carried out by this method consideration must be given to the effect it may have on the section to be left standing.

      In addition to its use in the final stages of the deliberate collapse method of demolition, pulling by wire rope may also be used for parts of buildings such as chimney stacks and walls without pre-weakening, other than perhaps partial removal by hand of the adjacent walling and ceiling (or) floor.

      The most suitable alternative methods are the use of demolition ball (or) pusher arm.

      Other mechanical methods include a number of specially designed hydraulically operated devices for demolition without the need for operatives to work at heights.

Use of explosives in demolition:

      Given the necessary expertise demolition by the use of explosives is possibly the safest method of demolition because the fewest people are at risk.

      Other precautions which need to be taken to prevent accidents when explosives are used in demolition operations are as follows:-

v  The competent person incharge of the operation, with the assistance of other experts    (eg. a structural engineer), as necessary should determine the further measures required for complete demolition.

Health hazards from demolition process arise from:

      Inhalation of toxic gases, vapours, fumes and dust

      Ingestion of corrosive (or) toxic liquids and dust

      Reaction with (or) absorption by the skin of corrosive, toxic (or) irritant dusts, powders, liquids, and chemical substances.

v  With regard to the danger from exposure to vibration, concrete breakers and pneumatic drills are examples of types of plant, widely used on demolition work, which may give rise to vibration white finger.

v  All demolition operations will create toxic asbestos dust and it is important to realize that no level of exposure, for any type of asbestos, has been accepted as being safe.

v  Silica may occur in natural stone(eg.stand stone) some backs and concrete aggregate and any method of demolition of structures constructed from there materials, will give rise to dust containing silica.

      Ammonia, chlorine and aniline are examples of gases and fumes that may be released during the demolition of refrigeration and chemical plant unless they have been properly purged before the demolition.

      Various toxic sludges may be encountered during demolition of virtually any storage tank forming part of an industrial process.

v  No demolition work that might endanger people on (or) near the site should be allowed until the contaminants have been identified and precautions taken.

Design aids for safe demolition:

      For the planner of demolition activities, the availability of accurate as constructed drawings in vital.

      When modifications to existing structures are required, when total demolition is contemplated (or) where there is evidence of failure (or) distress, the availability of accurate as constructed drawings and calculations will reduce the risk to people engaged in surveys and demolition tasks.

      Other permanent structures (eg.nuclear reactors) will have to be demolished within a foreseeable time span and their design should take into account not only the physical dangers to demolition workers but also the probable health hazards from contaminated materials.

      Most building and civil engineering works, however, are designed without regard to their eventual demolition.

      Nevertheless, energy project has its special circumstances and the designer is advised to discuss any possibility of partial (or) total demolition with the client (or) promoter.

      A study of british standard BS 6187code of practice for demolition and HSE guidance notes GS 29/1,29/2,29/3 and 29/4 will give the designer advice on planning, preparation, legislation and techniques for safer demolition.

      Advice is given on the hazards of some special demolition work which the designer may be able to alleviate in the original design.

      Demolition methods-BS 6187:1982 A guide to typical methods of demolition.

Methods of demolition:

      Detached building isolated site

      Detached building confined site

      Attached building isolated site

      Attached building confined site

For demolition work to erect the principal contractor must:

      Close the adjoining area

      Erect perimeter containment screening

v  Demolition work are now considered as construction work relevant people  doing demolition work on houses should implement control measures to prevent anyone from falling while doing the work.

v  Relevant people doing demolition work must hold a certificate to perform these activities and complete work method statements before starting any work.

v  Demolition work includes the:-

Ø  Demolition of a building (or) other structure (or) part of a building (or) other structure.

Ø  All demolition should be carefully planned and carried out by competent practioners.

Ø  The most common ways that soil is exposed to demolition activities.

Ø  Demolition work involves many of the hazards associated with construction.

Ø  However demolition incurs additional hazards due to unknown factors;deviations from the structure’s design introduced during construction, approved (or) unapproved modification that altered the original design, materials hidden with structural members, and unknown strengths (or) weaknesses of construction materials.

Ø  To counter these unknowns all personnel involved in a demolition project must be fully aware of these type of hazards and the safety precautions to take to control the hazards.

Ø  Demolition hazards are addressed in specific standards for the construction industries.

Ø  To eliminate risk during demolition through careful planning and design.

      Demolition we usually think of the process known as implosion.

      Most demolition, however is done with  more mechanical methods.

      One of the first steps in any demolition project is the removal of everything that is of value and can be salvaged.

      Glass would be removed to keep it from being turned into dangerous projectiles during the demolition.

      The implosion method of demolition is always thought of as the method of last resort.

      Although skilled demolition firms can safely implode a structure, it is considered a safety risk and is avoided if conventional demolition is practical.

      In most demolition jobs, the cleanup following the actual downing of the structure is them off time consuming part of the job.

      The need for demolition projects is unending as all structures have a limited life span.

      Currently many of the major housing projects built in the 1960’s and 1970’s are being demolished one by one to make room for new structures.

      Sometimes the demolition has a more uncontrolled connotation.

      It is like the demolition derby which is a wild and uncontrolled smashing of automobiles to see which is the last one running.

      True demolition is a carefully controlled process.

      Today even more environmental concern than even in being directed at demolition operations.

      As always, safety is the most important concern, but this idea of safety has been extended to the environment as well as the actual demolition process.

      BS 6187:1982 code for practice demolition.

Types of demolition:

      Manual-(pulling down) small storage building

      Mechanically-(pulling and breakdown)

Ø  Cranes

Ø  Excavators

Ø  Bulldozers

Ø  Wrecking ball-large structures

      Explosives-(implosion)

Ø  Explosive changes are placed in series and fenced in a controlled manner.

Safety in manual demolition:

      Manual demolition means stripping (or) demolishing by hand involving the use of physical strength and hand held tools.

Demolition by hand:

      Hand demolition involves the use of hand tools only,

Hazards in manual demolition:

      Penetrations

      Working at edges/height

      Uncontrolled collapse of structure (or) part of structure

      Noise hazards

      Sharp objects

      Electric shock (or) electrocution

      Dust and other filters

      Scaffold collapse

      Destabilized walls

      Falling hazards

      Hit, trap, crash hazards

      Hazards due to presence of hazardous material

Steps to taken for manual demolition:

      Engineering survey

      Develop a plan

      Removal of hazardous substance

      Removal of electrical lines

      Remove all the utilities

      Remove the fragile roof and glass

      Remove reusable materials

      Arrange for proper access, lighting, fire fighting system

      Allot a place for debris storage

      Enclose the nearest streets, roads

Key to safe demolition:

·         Pre-survey inspection

·         Method statement

·         Site supervision

·         Safe clearance zone

v  Pre-survey inspection:

 Providing information necessary to determine the method of demolition.

v  Site supervision:

 Not everyone on demolition can understand the structural significance of various components.

 Also such supervisor should have considerable knowledge on construction as well as in demolition.

 Anyone who is planning for demolition must be under the supervision of competent person(CHSW REG).

Safety in mechanical demolition:

      ‘Mechanical demolition’ means demolition by powered equipment other than hand-held tools.

      When demolition is to be performed by mechanical devices, such as weight ball and power shovels, the following additional precautions may be observed:-

Ø  While the mechanical device is in operation, no workmen shall be allowed to enter the building being demolished.

Mechanical demolition:

      Demolition with the ball

      Demolition by pusher arm

      Demolition by wire rope pulling

      Demolition by deliberate collapse

      Non-explosive demolition compounds

      Pressure jetting for concrete repairs

      Thermal lance technique

      Micro waves technique

      Concrete sawing

Hazards in mechanical demolition:

      Workers struck between the vehicles, balls etc

      Crane boom may touch the electric lines

      Crane may topple due to instability of soil and imbalance

      Boom may hit the nearest structures

      Debris may fall on the vehicle

      Boon failure

Explosion:

      Demolition using explosive is also otherwise called building implosion.

      Demolition by explosion (or) implosion.

Occupational hazard for demolition:

      Physical hazard (heat, cold, light, noise, vibration)

      Chemical

      Biological

      Mechanical

      Psychosocial

Preparatory before demolition:

      Copper wiring, are stripped from a building

      Glass materials should be removed

      Non-loading bearing partitions and dry wall are removed

      Electrical fittings to be removed

      Lifts, escalators to be removed

      Dispersion of dust to be analyzed

      Obtaining permission from the authority explosives is mandatory

Precaution before starting demolition work:

      On every demolition job, danger signs shall be conspicuously posted all around the structure and all doors.

      Ensure that no unauthorized persons shall enter the site of demolition for that a watchman employed and in addition to that he shall also be responsible to maintain all notice, lights and barricades.

      All gas, water, stream and other service line shall be shut off and capped before demolition work is started.

      All nails in any kind of lumber shall be withdrawn, hammered (or) bend over as soon as such lumber is removed from the structure being demolished.

General precautions:

      Manual demolition will be conducted on non-load bearing brick and timber walls and the roof.

      The building will be completely stripped leaving the skeleton of the building for mechanical demolition.

Exclusion zones:

      When designing for demolition using explosives need to plan for the possible fly of projectiles.

      People outside the exclusion zone should be safe from the demolition work.

OSHA standards:

      1926.859(a)- No workers shall be permitted in any area, which can be adversely affected by demolition operations

Personal protective equipment:

      Safety helmets and safety footwear must be worn at all times on demolition sites.

Before demolition:

      Shoring up of adjacent buildings

      Removal of rubbish and clearance of the site

      Disconnect, seal (or) remove any drainage under the building if requested to do so.

      Making arrangements with the statutory authorities to disconnect water and electricity supplies from the building.

      Inform the local fire authority if building (or) materials are to be burnt on site.

      Ensure that the site is adequately forced (or) otherwise secured to prevent dangers to those on (or) near the site.

      Demolition should be done in sequence, correct selection and use of appropriate processes, tools and equipment.

      Pre-wet areas to be demolished and building debris to be cleaned up to minimize dust.

4. Dismantling:

      Dismantling are high-risk activities whose safe execution is complex and technical and where expertise is vital.

      During dismantling, workers are injured in falls from edges and through openings and fragile surfaces.

      The CDM regulations apply to all dismantling work.

      The CHSW regulations requires that anyone planning (or) carrying out dismantling work must be under the supervision of a competent person.

      Ammonia, chlorine and aniline are examples of gases and fumes that may be release during the demolition of refrigeration and chemical plant unless they have been properly purged before the dismantling.

      Workers must be protected from falling when they dismantle supported scaffolds if protection is feasible and doesnot increase the risk of a fall.

      Those who dismantle scaffolds must have additional training from a competent person that covers dismantling procedures.

      Scaffolds must be dismantled only under the supervision of a competent person.

Hazard:

      Fall of person

      Fall of material

      Hit of object

      Slip, trip, fall

      The major risk and hazard activity is dismantling.

      All dismantling should be carefully planned and carried out by competent practioners.

      Dismantling of scaffolds should be done only under the supervision of a competent person.

      Anyone who is planning for dismantling must be under the supervision of competent person(CHSW REG).

5. Erection:

      Erecting of scaffolds should be done only under the supervision of a competent person.

Steel structure erection:

Hazard	Threat	Consequences	Control
Fall of material	Assembling of structure at height	Injury	Assemble steel structure parts on ground rather than at height Barricade area and prevent entry of people below the area where erection in progress

6. Hand tools:

v Hand tools can be a common source of accidents if used incorrectly.

v Five basic safety rules can help prevent hazards associated with the use of hand tools:

      Keep all tools in good condition with regular maintenance.

      Use the right tool for the job.

      Examine each tool for damage before use and donot use damaged tools.

      Use tools according to the manufacturer’s instructions.

      Provide and use properly the right personal protective equipment(PPE).

Hazards of hand tools:

      Hazards from the misuse (or) poor maintenance of hand tools include:-

Ø  Broken handles on files/chisels/screw drivers/hammers which can cause cut hands (or) hammer heads to fly off.

Ø  Incorrect use of knives, saws and chisels with hands getting injured in the path of the cutting edges.

Ø  Tools that slip causing slab wounds.

Ø  Poor-quality uncomfortable handles that damage.

Ø  Splayed spanners that slip and damage hands (or) faces

Ø  Chipped (or) loose hammer heads that fly off (or) slip.

Ø  Incorrectly sharpened (or) blunt chisels (or) scissors that slip and cut hands.

Ø  Dull tools can cause more injuries than sharp ones cracked saw blades must be removed from service.

Ø  Flying particles that damage eyes from breaking up stone (or) concrete.

Ø  Electrocution (or) burns by using incorrect (or) damaged tools for electrical work.

Ø  Use of poorly insulated tools for hot work in the catering (or) food industry.

Ø  Use of pipes (or) similar equipment as extension handles for a spanner which is likely to slip causing hand (or) force injury.

Ø  Mushroomed headed chisels (or) drifts which can damage hands (or) cause hammers( not suitable for chisels) and mallets to slip.

Ø  Use of spark-producing (or) percussion tools in flammable materials.

Ø  Painful wrists and arms(upper limb disorders) from the frequent twisting from using screw drivers.

Ø  When using saw blades, knives (or) other tools, they should be directed away from aisle areas and away from other people working in close proximity.

Hand tools safety consideration:

      Use of hand tools should be properly controlled including those tools owned by employees.

      The following controls are important.

Suitability:

      Using the correct tool for the job is the first step in safe hand tool use.

Inspection:

      The regular inspection of hand tools.

Training:

      All users of hand tools should be properly trained in their use.

      Always wear approved eye protection when using hand tools, particularly when percussion tools are being used.

Ø  Hand tools such as spades have to be used with great care to avoid further injury.

Ø  Hand tool injuries are relatively numerous in all branches of industry.

Ø  Too often there is failure to appreciate the importance of keeping hand tools in good condition and of eliminating the use of the wrong tool for the purpose.

Ø  Hand tools are not ordinarily thought of as dangerous agencies likely to produce injuries.

Ø  Actually, the use of hand tools in the manufacturing industries as a whole and in many individual industries is a major source of injuries.

Ø  Combined data from nine state labor departments, covering the years 1947 and 1948, assigned 7% of all permanent partial and the same proportion of temporary disabilities to the use of hand tools.

Ø  It is true that the proportion of permanent disability cases from the use of hand tools is low as compared to such cases in many other activities as, for instance, the operation of machinery.

Ø  Many fatalities result from use of electric-powered hand tools.

Ø  Hand tool injuries can be prevented as definitely as those from any other source, and it is just as profitable to prevent them.

Ø  Hand tools of one sort (or) another are used in every industry, more particularly in the metal-working trades, in maintenance and repair work, construction, logging and lumbering.

Control of accidents:

Ø  We can control accidents directly attributed to defective and improper hand tools, but we have more difficulty in controlling the action of the worker who might strike the tool a glancing blow, thus causing a piece of steel to fly at high velocity and strike his eye.

Ø  Blacksmiths must use care in tempering all hand tools, particularly those used for chipping (or) similar operations, because of the danger of pieces breaking off and flying.

Ø  Needless to say, material from which hand tools are made should be of good quality and appropriate for the use to which it will be put.

Following is a list of some commonly used power driven hand tools:

      Grinders

      Polishers

      Drills

      Nut and bolt drivers

      Hoists

      Portable exhausts

      Circular saws

      Small internal and external grinders

v  For simple jobs construction workers will use hand tools such as a hammer, screw driver, pliers, electric drills and screw guns.

v  Damage to the blood vessels and nerves in your hand and fingers can result from the long term use of powered hand tools.

v  The risk of conditions, such as Reynaud’s Syndrome, from powered hand tools is increased if you are also exposed to cold, because the cold causes you to use a much tighten grip in to the tool.

The hand tools may be:

      Hammer

      Crowbar

      Power tools

      Shovel

v  Employees should be kept sufficiently far apart in working areas to avoid injury from hand tools such as picks (or) shovels.