Coordinating trades and subcontractors

After the level 5 fall, Carla Mendes asked the foremen of all 14 trades then on site to meet in the trailer. She put a single question on the whiteboard: 'Who owns the guardrail around an opening?' The mechanical foreman said the scaffold company did, because it installed the rails. The scaffold foreman said whoever cut the opening did. The drywall foreman said Tallgrass did, because Tallgrass was in charge. Each answer was reasonable, and together they explained why a guardrail could be removed on a Saturday and stay off until Monday.

Coordinating the work of many employers is the prime contractor's central legal duty under section 7(3) of the Act. This lesson describes the tools Tallgrass uses to do it on Cottonwood Place.

Why coordination fails

Most coordination failures on construction sites come from a small number of patterns.

• Shared hazards with no owner. Guardrails, openings, temporary power, housekeeping on shared floors and access routes are used by everyone and maintained by no one unless someone is assigned.
• Stacked trades. Two or more trades working in the same space at the same time, especially one above the other, create hazards for each other: falling objects, blocked access, dust from one trade in another's breathing zone.
• Changes nobody hears about. A trade removes a guardrail, cuts an opening, isolates a circuit or moves a ladder, and the next trade does not know.
• Handovers that are not handovers. One trade finishes an area and another starts, but nobody checks the condition of the area in between.
• Schedule pressure. When the job falls behind, trades are pushed into areas before they are ready, and coordination meetings are skipped to save time.

The foremen's coordination meeting

Every Tuesday morning at Cottonwood Place, Carla chaired a one-hour meeting of every subcontractor's foreman. The agenda never changed: safety issues from the past week, the three-week look-ahead schedule floor by floor, shared hazards and who owns them, deliveries and crane time, and anything that needed another trade's help. Owen presented the week's inspection findings and open deficiencies. The meeting produced a short set of minutes with actions, owners and dates, posted on the site board and sent to every subcontractor's office.

The look-ahead was the key tool. Laying out three weeks of work by floor and zone on one sheet showed where trades would be stacked, where deliveries would block access, and where one trade's work, such as cutting openings or removing temporary protection, would affect another.

Assigning shared hazards

After Carla's whiteboard question, the foremen agreed on a list of shared hazards and wrote down who owns each one. The list went into the site safety plan as a revision.

Two new tools came out of that list. The opening register is a sheet for each floor, kept at the floor's stair tower, where any trade that plans to cut an opening must enter it in advance, with the size and the cover or rail that will protect it. The guardrail removal permit is a short form that any trade must get from Tallgrass's assistant superintendent, Ben Nakamura, before removing any section of guardrail. It states why the rail is coming off, what protection replaces it while it is off, who is responsible and when it will be reinstated. Ben checks each permit at the end of the shift.

Permit-to-work systems

The guardrail removal permit is one example of a permit-to-work system: a written authorization, issued by a responsible person, before a hazardous activity can start. Permits force the planning to happen before the work, make sure the people affected know about it, and leave a record. On Cottonwood Place, Tallgrass ran permits for hot work, confined space entry, energy isolation on permanent systems during commissioning, guardrail removal, critical crane lifts, excavation near utilities, and roof access during roofing. Each permit had a fixed form, a named issuer and a time limit.

Permits only work if they are issued with thought. A permit book where the superintendent signs blank forms at the start of the week defeats the purpose. Tallgrass audits a sample of permits each month against what was actually happening on site.

Stacked work and work above others

When the curtain wall crew began hoisting panels past floors 3 to 5, the look-ahead showed carpenters working at the floor 4 slab edge the same week, directly in the hoisting path. The coordination meeting moved the slab edge work to the following week and set an exclusion zone below the hoist on the days panels were lifted. Where stacking cannot be avoided, the trade above must protect the trade below with toe boards, debris netting or overhead protection, and the trade below must stay out of marked drop zones.

Owen uses a simple check to flag stacked work on the look-ahead before the meeting.

# Flag zones where incompatible activities overlap in the same week.
plan = [
    (1, "L5-north", "mechanical", "cut openings"),
    (1, "L5-north", "drywall", "board walls"),
    (1, "L4-east", "curtain wall", "hoist panels outside"),
    (1, "L4-east", "carpentry", "slab edge work"),
    (2, "L3-west", "drywall", "board walls"),
    (2, "L3-west", "electrical", "pull wire"),
]
conflicts = {("cut openings", "board walls"), ("hoist panels outside", "slab edge work")}
from collections import defaultdict
zones = defaultdict(list)
for week, zone, trade, act in plan:
    zones[(week, zone)].append((trade, act))
for (week, zone), items in sorted(zones.items()):
    acts = [a for _, a in items]
    for a in acts:
        for b in acts:
            if (a, b) in conflicts:
                print(f"week {week} {zone}: '{a}' conflicts with '{b}' -> resolve at meeting")

week 1 L4-east: 'hoist panels outside' conflicts with 'slab edge work' -> resolve at meeting
week 1 L5-north: 'cut openings' conflicts with 'board walls' -> resolve at meeting

The script only knows the conflicts it is told about; the meeting finds the rest. Its value is in making sure the obvious ones are on the agenda every week.

Handovers between trades

When a trade finishes in an area and another moves in, the condition of the area changes hands. Tallgrass requires a short walk between the outgoing and incoming foremen for any floor or zone handover, using a one-page checklist: openings covered or guarded, guardrails complete, temporary power safe, debris cleared, access clear, any hazards left behind identified. Both foremen sign. The checklist takes ten minutes and replaces the assumption that the last trade left things in good shape.

When a subcontractor does not cooperate

Most subcontractors cooperate readily, but the prime contractor's duty does not depend on their goodwill. Tallgrass's subcontracts require compliance with the Act, the regulation and the site safety plan, give Tallgrass the right to stop unsafe work and to remove workers who repeatedly break safety rules, and allow it to withhold payment or correct a hazard at the subcontractor's cost if the subcontractor will not. These clauses give Tallgrass the practical authority to carry out its legal duty to ensure compliance.

Communication that reaches every crew

Decisions made at the Tuesday meeting only protect workers if they reach the crews. Tallgrass requires each subcontractor's foreman to brief their crew on the meeting's safety items at their next toolbox talk and to sign the minutes to confirm it. Owen checks a sample each week by asking workers on the floors about the week's changes. When the guardrail removal permit started, he found that most crews knew about it within two days, but two crews that started on Wednesday had not heard, because their foremen had missed the meeting. Since then, any foreman who misses the meeting gets a short phone briefing from Ben the same day.

Site-wide changes, such as a new delivery route or a new muster point, also go on the site board, on signs where the change happens, and on a short text message to every foreman's phone. For urgent hazards, such as a high wind warning that stops crane work, Carla uses a group radio call followed by a text. The goal is simple: no worker should learn about a change by walking into it.

Coordinating with neighbours and the public

Coordination does not stop at the property line. The office building on the west side of Cottonwood Place had tenants who used the shared lane for parking and deliveries, and the street on the north side carried buses, cyclists and pedestrians. Tallgrass met monthly with the office building's property manager to share the look-ahead, warn of noisy or dusty work, and agree on lane closures. It gave the bus company advance notice of street closures for crane lifts. Its traffic plan, described in HSE-373, set out how pedestrians would be routed around the site safely. When the curtain wall hoisting started, Tallgrass notified the office tenants whose windows faced the lift zone and agreed that blinds would be closed during lifts.

When coordination meets the schedule

The biggest threat to coordination is schedule pressure. When Cottonwood Place fell three weeks behind after a wet spring, the owner asked whether trades could be stacked more heavily to catch up. Carla and Owen did not refuse; they planned it. They identified which floors could safely hold two trades at once, added a second shift for some work so that trades could be separated in time rather than space, added overhead protection where work had to be stacked vertically, and increased Ben's daily floor walks from one to two. The plan was presented to the owner with its costs. The job recovered two of the three weeks, and the extra measures were recorded in the site plan as revision 6.

The lesson Carla draws from that period is that schedule recovery is itself a high-risk activity and deserves its own plan. The worst outcome is not a late finish but an injury caused by trades pushed together without anyone thinking through how they will affect each other.