Civil engineering and building construction projects require not only skilled labor but also heavy equipment such as cranes, concrete pumps, hydraulic excavators, and dump trucks, among others. The use of this machinery requires that it be operated in accordance with CNESST safety regulations, the manufacturer’s instructions, and the recommendations of professionals, such as structural engineers and geotechnical engineers. Failure to comply with all of these safety measures can result in injuries, property damage, and even more serious disasters, including the death of workers.

On construction sites, depending on the number of workers and the cost of the project, a health and safety representative is present:

• Part-time, for sites employing between 10 and 99 construction workers at any given time during the project;
• Full-time, for sites employing at least 100 construction workers simultaneously at any given time during the project, or for projects costing more than $12 million.

The presence of this qualified representative will ensure that a prevention program is implemented and that CNESST health and safety regulations are enforced. Qualified heavy equipment operators must normally be familiar with the operation and limitations of the equipment, as well as the safety rules prescribed by the manufacturer. Professionals must issue warnings, as appropriate, regarding situations that could endanger workers and the public. Contractors are also responsible for ensuring that the health and safety program is followed by personnel on their job sites.

Here are a few examples of non-compliance with one of these requirements:

First Case

For a project to replace a culvert located at a depth of 27 to 30 meters, the soil mechanics engineer indicated in his geotechnical study report that the deep soil consisted of sensitive clay. He recommended providing a minimum slope of one vertical to two horizontal and neither storing any materials nor allowing machinery to operate within a distance from the top of the excavation at least equal to its depth. As for the slopes in the area where excavation had been completed, the contractor had graded them to comply with the requirements of the geotechnical study.

However, as shown by the blue line in Figure 1, dump trucks on the job site, once loaded by the excavator, traveled along the crest of the excavation, which is contrary to the geotechnical engineer’s recommendations. In addition, the hydraulic excavator was positioned at the top of the slope, whose gradients had not been graded according to those specified in the geotechnical study.

In this case, the result was a disaster that could have led to serious injury or even death for the machine operators. In fact, stability analyses of the excavation slope revealed that, without the repeated passage of trucks at the top of the excavation, the slopes were stable with a slight safety margin. However, this margin was completely eliminated by the passage of trucks to the point where the stability of the excavation slope was compromised (see Figure 2).

Second Case

Furthermore, following an incident at the L’Épiphanie quarry that received media attention in 2013, the CNESST investigation concluded the following:

Just as in the first case, planning construction site operations and following the recommendations of professionals—when they were involved—are essential to establishing adequate work procedures to ensure safety on the job site.

Third Case

As a final case, we will examine an example of liability when an external supplier is called upon to operate heavy equipment on the job site through a general contractor. This case involves a concrete pump supplier with an operator, whose services were retained by a subcontractor hired by the general contractor to perform formwork and foundation pouring work.

To provide some context, the area for the foundation footings had been excavated in clay soil; then, to facilitate traffic on the job site, a layer of crushed stone (0–20 mm) approximately 0.3 meters thick was placed over the clay layer.

The operator reportedly received no information regarding the nature of the ground on which the crane was positioned. Relying on a quick reference chart on board the crane for selecting the ground support conditions for the outriggers, the operator chose a configuration that, on the surface, corresponded to ground consisting of crushed stone fill. The entire site was covered with crushed stone fill, even in the pits where the foundation footing formwork was located. In Figure 6, we can see that the rear left support of the pump had sunk into the ground.

According to the concrete pump’s safety and operating manual, the operator must consult with site management regarding the bearing capacity of the ground. If the bearing capacity is unknown, the operator must assume the worst-case scenario. In doing so, the size of the support plates must be determined based on the most restrictive configuration.

Since the operator had not received any information regarding the bearing capacity or the nature of the ground, the worst-case scenario should have guided the selection of support conditions for the pump’s stabilizers, rather than the presence of the layer of stones visible on the surface. The presence of a clay layer with low bearing capacity, beneath a layer of crushed stone that was too thin to distribute the pressure exerted by the concrete pump’s support on the clay, would explain why the stabilizer sank into the ground, leading to its overturn.

Conclusion

In these three cases, we have seen the consequences of failing to follow professional recommendations, carrying out work with inadequate planning and supervision, and, finally, using equipment without heeding the manufacturers’ instructions regarding the basic rules they prescribe in their manuals.

When an accident occurs on a construction site, Origin’s civil engineering experts are able to investigate and identify the causes of such an event, particularly those related to the use and operation of heavy equipment.

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Please note that the term “workers” is used generically and includes female workers.