Construction work and the public
Construction sites create risks not only for the construction worker, but also for members of the public where the construction work is carried out on a site that is near or adjacent to the property boundary or to any public place. Some examples of the hazards created are:
- changes to surface levels;
- excavations, holes and trenches;
- falling material and debris;
- plant and equipment;
- dust vapours or other hazardous substances;
- vibration; and
- site visitors.
The general public must be protected from the hazards associated with construction work that may be carried out in a public area or adjacent to such an area.
The Occupational Safety and Health Act 1984 (OSH Act) requires that care be taken at work by employers, employees and self-employed people to ensure that no members of the public or workers are exposed to hazards as a results of their work. Refer to Section 21 of the OSH Act for more information.
Regulations 3.75 and 3.76 of the Occupational Safety and Health Regulations 1996 clearly explain what must be done to protect people who are in the vicinity of, but are not on, the construction site. AS 2601 - Demolition of Structures requires all demolition sites to be fenced in.
Current methods of protecting the public
The first step in any construction project with regard to public protection is the identification of hazards and the planning of the best methods of eliminating or controlling the hazards. The Builder / Project Manager / Supervisor etc must incorporate the following in their Safety Management plan for the project.
- identification of the hazards to the public;
- evaluate the risk of harm those hazards create;
- define construction methods and prescribe physical safeguards to avoid or reduce injury and prevent property damage;
- inform all levels of management of the degree of risk: and
- ensure appropriate training is implemented.
Hierarchy of control
In the assessment of the hazards the control measures implemented should follow the hierarchy of control. This being:
- elimination - removing the hazard from the workplace. This is the most effective control measure;
- substitution - substituting or replacing a hazard or hazardous work practice with a less hazardous one;
- isolation - isolating or separating the hazard or hazardous work practice from people involved in the work and members of the public.
This can be achieved by:
- providing overhead protection in the form of a gantry or enclosed scaffold.;
- engineering if the hazard cannot be eliminated, substituted or isolated, an engineering control is the next preferred measure. This may include modifications to plant or equipment, providing guarding to machinery or equipment;
- administrative - introducing work practices which limit exposure - eg road/footpath closure or working on weekends to limit public exposure.
The location of a project will dictate the amount and degree of public protection required.
In assessing the risks to the public it is also essential to analyse who would be at risk and how, eg age factors, physical impairments etc.
The proximity and type of adjoining properties must be taken into account in assessing hazards. For example a school located nearby will provide a large number of children who are intrigued by construction sites. If the site location is in a business district, pedestrian movement would also be high.
Construction work which affects the stability of adjoining structures must also be assessed to ensure that the structural integrity of the buildings alongside are maintained. The construction methods used may also create hazards. For example the use of sheet piling may provide a noise and vibration nuisance.
If traffic disruption is expected the impact to the traffic flow must be assessed. The volume of traffic flow and times of day of such flow are also important. For example on a busy major arterial road the disruption to traffic flow on weekdays may preclude such work. The implication of this may be that only weekend access is viable. The planning of operations on site therefore becomes imperative as prudent access scheduling can minimise traffic disruption. The implementation of a traffic management plan is paramount in this situation.
Types of hazards (current protective measures)
Changes to surface level, excavations, holes and trenches
Site works, footpath alterations, etc often create hazards to the public, which can easily be eliminated or controlled by the following:
- erection of barriers around hazards;
- display of warning signs and caution lighting where necessary;
- arrange for a traffic/person controller to redirect traffic/people;
- provide a temporary by-pass for traffic/people;
- provision of additional lighting at night;
- where the construction process breaks into security fenced areas such as electrical
- switchyards, swimming pools, chemical storage yards etc, temporary fencing must be provided to maintain security;
- ensure excavations across driveways and roadways are backfilled before the end of a working day. If this is not possible provide safe access across the excavation;
- maintain vigilance during work breaks eg ensure a controller is in position during breaks; and
- providing level pedestrian and wheelchair access around the area.
Falling material and debris
Falling materials and debris can cause serious injury to members of the public. If there is a risk of an object or material used in construction work falling, onto people who are likely to be in the vicinity of, but not on the construction site, the main contractor at the construction site must ensure that overhead protection is erected that will catch, deflect or hold any weight and amount of material or objects that might reasonably be expected to fall onto it. . Measures which can be implemented to alleviate the hazard of falling material and debris are:
- the erection of a gantry-(overhead protection);
- the use of enclosed scaffold with catch platforms;
- the erection of hoarding or barricades;
- the use of chutes for discharge of debris;
- clear area maintained around perimeter of building; and
- scheduling of work to minimise risk.
Plant and equipment
Plant and equipment are an essential part of most construction projects. Their movement to, around and on construction sites creates hazards. The public can be isolated by the following measures:
- enclosure of entire construction site via fencing;
- display of warning signs/lights;
- arrange for a controller to redirect traffic/people;
- provide a temporary by-pass for traffic/people;
- erection of barriers around work area;
- use of spotters working with the plant; and
- locking of site at night and tagging out of all plant and equipment.
Dust and hot work
The following measures can control dust and hot work:
- water to control dust nuisance;
- welding screens;
- hoardings to prevent the passage of dust, sparks etc;
- programming of work to suit environmental conditions - eg site clearing on a windy day :or
- stabilising the ground with spray-on cellulose fibre.
Vibration and noise
Noise and vibration often provide more of a perceived hazard to the public than actually cause physical damage. Methods of controlling noise and vibration are:
- use of attenuated machinery;
- provision of acoustic barriers; or
- use of smaller machinery to lessen vibration;
Preventing public access to the site can alleviate the majority of hazards. Effective measures of preventing public access are:
- provision of total site fencing;
- provision of security personnel to site;
- monitoring access/egress points to site;
- if working in occupied premises ensuring that all staff are briefed on where they may access; and
- warning signage.
Physical types of public protection (currently required by the regulations)
The most common method of public protection utilised is physical separation of the public from the construction work. Essentially this method separates the public from the hazard thus isolating it. Other methods, such as gatemen or signage, should only be used in addition to physical separation.
There are five basic types of physical public protection: barricades, hoardings, gantries, scaffold and fences. The uses of these methods of public protection, and some acceptable alternatives are described below.
Barricade (regulation 3.75)
A barricade means a temporary barrier erected from rigid vertical and horizontal members similar to crowd control barriers. The horizontal guardrail is between 900mm to 1100mm from the ground level. It is used when it is necessary to exclude members of the public from a temporary construction site or work area. A plastic safety mesh barrier 900mm in height attached to star pickets is an acceptable alternative to a rigid barricade for protection around excavations.
Barricades erected adjacent to roads also require warning lights to alert motorist of the hazard during night or inclement weather.
Hoarding (regulation 3.75)
A hoarding means a substantial and fully sheeted screen a minimum of 1.8 metres in height. It should be used where a greater measure of protection is necessary or where construction work is of a more permanent nature. For example, a hoarding is often used on a demolition site to exclude members of the public and to prevent debris from spilling or rebounding out of the site.
Scaffold (regulation 3.67)
A scaffold can be utilised to provide public protection. A scaffold can be constructed to ensure that no materials or dust will leave the working platform.
This can be achieved by ensuring the scaffold has the external face and ends sheathed with a fire retardant material and wire mesh that has wires that are at least 3mm in diameter and with apertures not greater than 50mm x 50mm:
- Where further protection is required the scaffold should have at the first stage a catch platform not less than 2 metres in width projecting at an angle of 45 degrees from the vertical extending along the outside and returned at both ends.
- A hoarding attached to the outer standards that extend to the underside of the catch platform.
- Night-lights that provide adequate illumination at both ends and under the platform.
Scaffold used in demolition work must be heavy duty (regulation 3.128)
- a person who, at a workplace, is an employer, the main contractor or a self-employed person must ensure that any scaffold involved in demolition work at the workplace, other than class 1, class 2 or class 3 demolition work;
- is a heavy duty scaffold that meets the requirements of AS/NZS 1576.1;
- is erected to the full height of the building or structure;
- has a closely boarded platform with a minimum width of one metre that abuts on the face of the building or structure at the working level;
- has a fender board not less than 900 mm high fitted on the outer edge and on the ends of the working platform;
- has the external face and ends sheathed with a fire retardant material and wire mesh that has wires that are at least 3 mm in diameter and with apertures not greater than 50 mm x 50 mm;
- is maintained in position and in an effective state up to the working level of the scaffold for the whole of the period during which the demolition work is being done; and
- is progressively dismantled so that the unsupported part of the scaffold does not exceed by more than 4 metres the height of the last row of ties that secure the scaffold to the building or structure.
A licensed demolition contractor must ensure that any scaffold involved in class 1, class 2, or class 3-demolition work complies with regulation 3.128.
Gantry (regulation 3.76 and 3.77)
If there is a risk of an object or material used in construction work falling, whether from a crane or otherwise, onto people who are likely to be in the area that is in the vicinity of, but not on the construction site, the main contractor at the construction site must ensure a gantry is erected in the area.
'gantry' means a structure that is used:
- for the overhead protection of people;
- for the support of materials and people:and
- capable of withstanding all intended loads.
The main contractor at a construction site must ensure that the design, erection, use and maintenance of a hoarding, barricade or gantry at the site is such that, having regard to the construction work to be done, the hoarding, barricade or gantry is self supporting and can withstand the loading, if any to be placed upon it.
The following is guidance for gantries constructed from steel scaffold tubing and fabricated steel. Gantries constructed of fabricated steel must be engineer designed.
- The gantry should extend the full length of the building and where possible extend at least 2 metres past the ends.
- Head clearance minimal distance of 2.1metres from the footpath to any horizontal member.
- Standards/columns no closer than 300mm to the edge of the kerb.
- Standards founded on base plates and sole boards.
- Standards/columns painted white to a height of 2.1 metres.
- Braced or tied to substantial ground anchors or otherwise secured from overturning.
- Main decking covered by an independent water proof cover of metal or other material that is capable of effectively shedding the water.
- The cover must slope towards the construction site.
- A continuous handrail on the outer standards fixed at not less than 900mm and not more than 1100mm above the main deck.
- The area between the main deck and the top rail to be enclosed with scaffold planks or material of similar strength.
- Night-lights that provide adequate illumination at each end and under the gantry.
- A hoarding attached to the inner standards that extends to the underside of the decking.
- Any scaffold fittings or sharp protruding objects must be protected or wrapped.
- A gantry may be removed and replaced with a hoarding or barricade when the need for overhead protection no longer exists.
A 1.8 metre high link mesh is an acceptable alternative to a hoarding if the only requirement is to secure the site from members of the public. The fence should be erected to all elevations of the site.
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