How a construction site is organized and who is in charge

A construction site is a workplace that builds itself out of existence. Every week the floors, walls, openings, roads and hazards change. The crew that poured the footings is gone by the time the roofers arrive, and the electricians who pull wire through the third floor in March were not on site in January. People from a dozen or more employers work side by side, often within arm's reach of a hazard created by someone else. That is why construction, year after year, has one of the highest rates of serious injury and death of any industry in both Canada and the United States, and why construction safety starts with a simple question: who is in charge of what?

This course gives every worker on a construction site, whatever their trade and however new they are, a clear picture of how a site is organized, the hazards that injure and kill construction workers most often, and the daily routines that keep those hazards under control. It sits between two other courses. TRD-101 Construction and Trade Safety follows a first-year apprentice learning the basics of a trade. CON-355 Safety Leadership for Site Supervisors is written for the superintendents and foremen who run the work. HSE-370 is the safety-stream view of the whole site: what any worker, from a general labourer to a visiting delivery driver, needs to understand to work safely among many trades.

The project in this course

This course and the five that follow it, HSE-371 to HSE-375, use one invented project. Cottonwood Place is an eight-storey mixed-use building in Winnipeg, Manitoba, with shops on the ground floor, seven floors of apartments above and one level of underground parking. The site is tight: a busy street on the north side, a lane on the east, an occupied office building on the west and a parking lot on the south that serves as the laydown and trailer area. A tower crane stands in the middle of the footprint. At the busiest point of the job, about 140 workers from 18 employers are on site on a single day.

The general contractor is Tallgrass Construction Ltd., which is also the prime contractor for the site. The people we will meet most often are:

• Carla Mendes, Tallgrass Construction Ltd.'s site superintendent, who runs the site day to day.
• Owen Hartley, Tallgrass Construction Ltd.'s site safety coordinator, who runs orientations, inspections and the safety program.
• Dev Sandhu, a general labourer with Tallgrass Construction Ltd. who started on the project this spring. Much of the course follows his first months on site.
• Lena Petrov, a formwork carpenter with a concrete forming subcontractor, who is the workplace safety and health committee worker representative.
• Marco Silva, foreman for Silva Earthworks, the excavation and underground services subcontractor.
• Tasha Brooks, foreman for the electrical subcontractor.
• Ray Lindqvist, the tower crane operator.

How construction differs from other workplaces

In a factory, the building, the machines and the work processes stay much the same from year to year. Hazards can be studied, guarded and written into procedures that last. A construction site is different in at least five ways, and each of them shapes how safety has to work.

• The site changes every day. A floor edge that was protected by a wall yesterday may be open today because the wall panel was removed to bring in materials. A ramp that was safe on Monday is mud after Tuesday's rain. Hazard assessments have to be repeated far more often than in a fixed workplace.
• Many employers share one site. Each subcontractor has its own workers, supervisors, tools and habits. A hazard created by one employer, such as a hole cut in a deck by the plumbers, can injure the workers of another employer, such as the drywall crew who walk past it.
• The workforce turns over constantly. Trades arrive and leave as the job moves through its phases, and individual workers come and go. On a typical day at Cottonwood Place, several people are on site for the first time.
• Much of the work is at height, below grade or near heavy equipment. Falls, trench collapses, being struck by vehicles or loads and contact with electricity are built into the work itself.
• Schedules are tight and weather matters. Pressure to finish before winter, before a concrete pour or before the next trade arrives pushes people toward shortcuts.

None of this makes construction injuries inevitable. It means that safety on a construction site depends on organization: clear roles, shared rules, good communication between employers and routines that are repeated every day.

The parties to a construction project

Several organizations have a hand in every project, and each has a part to play in safety.

The prime contractor

When two or more employers work on the same construction project site, Manitoba's Workplace Safety and Health Act requires one of them to be the prime contractor. The prime contractor is usually the general contractor, and the role is often named in the contract between the owner and the contractor. If no one is named, the duty can fall on the owner. The prime contractor's job is coordination. It must make sure that the activities of all the employers and workers on the site are organized so that no one is endangered by the work of someone else, and that there is a system in place for meeting the law across the whole site.

At Cottonwood Place, Tallgrass Construction Ltd. meets its prime contractor duties in several ways. It runs one orientation for everyone who comes on site, whatever their employer. It sets site rules that apply to all employers, such as where vehicles may drive and the rule that every open edge is guarded. It holds a weekly coordination meeting where foremen plan the next week's work and spot clashes, such as the crane swinging loads over the area where the electricians are working. It inspects the whole site every week and follows up with the employer responsible for each hazard found. And it keeps a list of every employer on site, with the name of its supervisor and its own safety documents.

Coordination does not take responsibility away from anyone else. Each subcontractor is still the employer of its own workers and still has to train them, supervise them, give them the right equipment and follow the law. When Silva Earthworks digs a trench, Silva Earthworks must make sure it is sloped or shored. Tallgrass Construction Ltd.'s role is to check that it is, to stop the work if it is not, and to make sure the trench does not create a hazard for anyone else, such as a delivery driver backing toward an unguarded edge.

Employers, supervisors and workers

The law spreads duties across everyone on the site. Under Manitoba's Workplace Safety and Health Act, every employer must ensure, so far as is reasonably practicable, the safety and health of its workers. That includes providing safe equipment and materials, safe work procedures, training and supervision, and the protective equipment the work requires. Employers with 20 or more workers need a written safety and health program. Supervisors must make sure their workers follow the law and the safe work procedures, and must tell them about every hazard they know of. Workers must take reasonable care to protect themselves and others, use the protective equipment provided, follow the safe work procedures and report hazards to their supervisor.

In practice, the foreman is the person whose behaviour matters most to a new worker. Foremen decide how the work will be done, who will do it and with what equipment. They notice when someone is struggling, when a shortcut is being taken and when conditions have changed. At Cottonwood Place, Carla Mendes tells every new foreman the same thing at their first coordination meeting: "Your crew will do what you do, not what you say. If you walk past an open edge, so will they."

The three rights of every worker

Manitoba law, like the law in every Canadian province, gives workers three basic rights. The right to know means being told about the hazards of the work and how to protect yourself, through orientation, training, WHMIS labels and safety data sheets. The right to participate means having a say in health and safety, mainly through the workplace safety and health committee or a worker representative, and through reporting hazards and taking part in inspections. The right to refuse means a worker may refuse work they reasonably believe is dangerous to themselves or others, without being punished for doing so. Lesson 12 explains how a refusal works on site.

Committees and representatives

Workers have a formal voice in safety through committees and representatives. In Manitoba, an employer that regularly employs 20 or more workers at a workplace must have a workplace safety and health committee, with at least half its members chosen by the workers. A workplace with five to 19 workers designates a worker safety and health representative instead. On a construction site, the prime contractor usually runs a site committee that brings together worker members from several employers, because a hazard on a shared site is everyone's business. At Cottonwood Place, the committee meets monthly, walks the site before each meeting, reviews every incident and near miss, and sends written recommendations to Carla Mendes, who must respond.

Lena puts it plainly to new workers: "If you see something and don't want to raise it with your own foreman, tell me. I'll take it to the committee and nobody needs to know it came from you."

A site with many employers: how the pieces fit

On a shared site, most serious hazards sit at the boundaries between employers. The earthworks crew leaves a trench edge unguarded when it finishes for the day. The plumbers cut a hole in a deck and cover it with a sheet of plywood that is not secured or marked. The crane lifts a bundle of rebar over a lane where the masons are working. In each case, the employer that created the hazard is not the employer whose workers are exposed to it.

Cottonwood Place handles these boundaries with a few simple systems that later lessons look at in detail:

• One orientation for all, so every worker knows the site rules, the emergency plan and where the hazards are, whoever their employer is.
• A weekly coordination meeting and a daily look-ahead, so foremen know what the other trades will be doing next to them.
• Work permits for the highest-risk activities, such as hot work, cutting into a deck, excavation near the occupied building and crane lifts over the lane.
• Shared inspections and a single hazard log, so that a hazard found by anyone is assigned to the employer who must fix it, with a date.
• A clear rule that anyone can stop unsafe work, whoever's work it is.

Counting who is on site

Knowing who is on site matters for two reasons. In an emergency, the prime contractor needs to know who to account for. And the number of new workers on site is one of the best warning signs of risk: workers in their first weeks on a job are injured at much higher rates than experienced workers on the same site. Owen Hartley keeps a simple count from the sign-in records. The program below uses invented sign-in data for four weeks of the job to find the peak number of workers and the share who were in their first week on site.

# Cottonwood Place sign-in summary (invented data): workers on site and first-week workers.
weeks = {
    "Week 14": {"on_site": 96,  "first_week": 21},
    "Week 15": {"on_site": 118, "first_week": 30},
    "Week 16": {"on_site": 141, "first_week": 34},
    "Week 17": {"on_site": 133, "first_week": 12},
}
for wk, d in weeks.items():
    share = d["first_week"] / d["on_site"]
    flag = "  <- extra supervision" if share >= 0.2 else ""
    print(f"{wk}: {d['on_site']:3d} on site, {d['first_week']:2d} new ({share:.0%}){flag}")
peak = max(weeks, key=lambda w: weeks[w]["on_site"])
print("Peak week:", peak, "with", weeks[peak]["on_site"], "workers")

Week 14:  96 on site, 21 new (22%)  <- extra supervision
Week 15: 118 on site, 30 new (25%)  <- extra supervision
Week 16: 141 on site, 34 new (24%)  <- extra supervision
Week 17: 133 on site, 12 new (9%)
Peak week: Week 16 with 141 workers

In weeks 15 and 16, when the mechanical and drywall subcontractors arrived, roughly one worker in four was new to the site. Tallgrass Construction Ltd. responds to weeks like these by running extra orientation sessions, asking each subcontractor to pair new workers with an experienced worker for their first week, and having Owen Hartley walk the floors where the new crews are working.