Guidelines released to manage concrete pumping risks in construction

In December 2021, a concreter suffered serious injuries including a cervical spinal fracture and lacerations to his head and body after being struck by a mobile concrete placing boom at a residential construction site. The concreter was part of a team pouring a house slab. Early investigations indicate that one of the mobile concrete pump’s outriggers moved off its dunnage while operating, sinking into the adjacent ground. This appears to have resulted in the concrete pump’s boom moving in an uncontrolled manner, striking the concreter. There were two more incidents in March 2022, where mobile concrete placing booms overturned; while no injuries were recorded, there was significant damage to both buildings and plant. Investigations into both incidents are continuing.

There are numerous risks associated with the setting up of concrete pumping equipment, including mobile concrete pumping booms tipping over and the risk of workers being crushed or run over by the mobile concrete pump itself. Ground conditions can also vary from one workplace to another, and even within a sit itself over time. Saturated earth will also reduce the bearing capacity of the ground. Failure to address poor ground conditions may cause the plant to overturn and result in serious injury to the concrete pump operator and other people nearby.

Factors that affect the ground providing adequate support include water, particularly when it is mixed with the soil as mud, and where it is present under the surface. Additionally, the type of ground (clay, sand, rock or a mixture of these), back-filled ground that was previously an excavation or trench, cavities of penetrations that have been converted but still exist, and continued operation of the concrete pump in one location can also affect the ground and its ability to provide adequate support. Ground slope can also reduce the stability and cause the concrete pump to move off supports during use.

Taking steps to manage risks is a condition of doing business in Queensland. If an incident occurs, business owners and operators will need to show the regulator that they have used an effective risk management process. This responsibility is covered by the primary duty of care in the Work Health and Safety Act 2011. Business owners and operators are advised to use the hierarchy of controls to determine how to eliminate and reduce risks in the workplace. The hierarchy of controls ranks types of control methods from the highest level of protection and reliability to the lowest. Business owners and operators should work through the hierarchy of controls when managing risks, with the aim of eliminating the hazard, which is the most effective control.

The Work Health and Safety Regulation 2011 includes duties for persons conducting a business or undertaking (PCBUs) with management or control of a construction workplace, plant, powered mobile plant and plant that lifts or suspends loads. Those who own concrete pumping plant must ensure management or control of that plant, with duties to eliminate or minimise the risks associated with that plant. Planning for concrete pumping operations should start as early as possible in the development of any work or project to help eliminate the associated health and safety risks. Consultation with all people engaged in the work, including the principal contractor, the concrete pumping PCBU, electricity entity, designer and project manager is essential.

When planning for concrete pumping operations, there are several issues to be considered, including proximity to overhead powerlines, concrete pumping requirements (including concrete pump selection, concrete delivery and site access) at the project design stage and the development of an emergency plan for each workplace where concrete pumping work will be done. Additional safety observers should also be used, depending on the size and complexity of the work. Ground support capacity and slope should also be assessed, with enough space provided to avoid short legging the outriggers (short legging is a practice that should be avoided wherever practicable due to the increased risk of overturning the mobile plant. The Concrete pumping code of practice 2019 outlines the roles and responsibilities associated with concrete pumping operators, including concrete pump owners and concrete pumping operators.

Concrete pump owners must ensure that pads and/or timbers supplied with the concrete pumping equipment will adequately support the plant. The owner may need to seek the advice of a competent person when selecting appropriate materials to support the outrigger feet. Before and during concrete pumping operations, the concrete pumping equipment operator must complete the daily inspection checklist, including filling out the logbook. For mobile concrete placing booms, the outriggers should be set according to the manufacturer’s operating instruction for the specific type of mobile concrete pump. The concrete pumping equipment operator must monitor the safe use of the concrete pump, concrete delivery lines and boom. For mobile concrete placing booms, operators should monitor the safe support of the carrier, including observing the outrigger pads and the ground. Operators must also be in view of the line hand and monitor the safe delivery of concrete.

When setting up a concrete pump, the area should be level, capable of supporting the load and free of obstructions, with precautions taken when a concrete pump is used in the vicinity of an excavation. The concrete pump should not be positioned over or adjacent to previously disturbed ground that’s been back-filled, excavations, trenches or holes in the ground, cellars, basements or pits, and inadequately compacted or soft ground. If the ground is near an excavation, the pump operator should refer the matter to the principal contractor for relocation to a more stable location. When the concrete pump is continuously operated in one location, the ground must not be compacted to the extent that the pump is likely to overturn. The pump unit must be set up level and if this is not possible, operators must ensure that the incline or angle of the machine does not exceed the manufacturer’s recommendations, per the operating manual. When setting up close to concrete pads/pavement, operators must also be aware that the ground could be softer due to rain water run-off and/or the ground being disturbed.

When setting up outriggers, supply members (such as timbers) must have a large enough area. Operators must ensure that outrigger pads are clear of excavations, soft or filled ground, or other obstacles liable to interfere with the safe operation of the machine. The members (timbers) must also have sufficient bearing area to support the machine. Operators must ensure that the outriggers do not subside by making regular checks of stability. Timbers, pads and steel plates should be of dimensions and material as specified by the concrete pump manufacturer (if the manufacturer has not provided this information, a competent person such as an engineer, should specify the minimum size of the material to be used).

When setting up outrigger timbers on sloping ground, the ground should be cut and the timbers set up so that they are level. The timbers should not be laid on sloping ground, as the outrigger feet can slide off the timbers. The timbers should not be bridged over timbers underneath, as this increases the bearing load on the ground. Outriggers must also be set up in accordance with the plant manufacturer’s instructions.

The ground-bearing capacity must be greater than the maximum pressure applied by the mobile plant to the ground, to ensure the plant does not sink or overturn. If not, then appropriate control measures, such as increasing the area of the outrigger pads or carrying out earthworks to increase the ground’s bearing capacity, should be implemented. Some concrete pumping boom manufacturers provide information on the maximum force applied by outriggers and the minimum area of outrigger pads to be used.

Information, training instruction or supervision for concrete pumping operations should address the method for inspection and maintenance of concrete pumping equipment, knowledge of the manufacturer’s operation and service manuals, the work methods to be used in the setting up and safe operation of concrete placement booms and pumps, and the correct use, care and storage of equipment to be used, including electrical safety practices.

Supervisors must ensure that workers who have received training and instruction are authorised to carry out work, and monitor the work sufficiently to ensure that safe work practices are being carried out, including the use of all protection systems and personal protection equipment. When pumping concrete, workers must wear safety helmets, eye protection, a safety vest and rubber safety boots. The control measures put in place must also be reviewed regularly to make sure they work as planned.

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