Rebar Column Work at a Leading Edge
A crew is tying vertical rebar for 12 bridge pier columns. Each column is 18 in. square and rises 14 ft above a concrete deck. Workers stand on a 4 ft wide plywood platform clamped to the column at 8 ft; the river-side edge has no guardrail because formwork occupies that side. The site fall protection plan allows personal fall arrest systems (PFAS). A worker wears a full-body harness and a 6 ft shock-absorbing lanyard anchored to a rebar hoop at the worker's shoulder height. The platform is 12 ft above a concrete footing; beyond the footing the drop to the river is another 9 ft. The lanyard's maximum deceleration distance is 3.5 ft, and the worker is 5 ft 10 in. tall. Site policy requires 2 ft of clearance above any lower level. The foreman wants to proceed with the afternoon pour and asks whether the PFAS is acceptable as rigged.
1. Calculate the minimum fall clearance needed for the system as rigged and decide whether the worker can safely use it above the footing. Show each component of the calculation.
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Use the clearance equation: required clearance = free fall + deceleration distance + worker height + safety margin.
- Free fall: the lanyard is 6 ft and the anchor is at shoulder height, so the worker can fall about 6 ft before the lanyard tightens. If the anchor were overhead, free fall would be reduced, but it is not.
- Deceleration: 3.5 ft.
- Worker height: 5 ft 10 in. = 5.83 ft.
- Safety margin: 2 ft.
Total = 6 + 3.5 + 5.83 + 2 = 17.33 ft.
Only 12 ft is available to the footing. The worker would strike the footing before the lanyard completed arrest, so the system is not acceptable as rigged. The additional 9 ft drop beyond the footing makes the consequence worse. Stop the pour until a guardrail system or a PFAS with a verified overhead anchor and adequate clearance is installed.
2. Identify at least three alternative controls and rank them by effectiveness for this task.
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Rank controls from most to least effective:
- Guardrail system on the work platform. This eliminates the fall exposure and does not depend on worker behavior or clearance below. A toprail, midrail, and toe board on all open sides would be the preferred control.
- Work platform or aerial lift with guardrails. If the platform cannot be guarded, use equipment designed for the task that provides a guarded work surface. Verify the lift is rated for the surface and slope.
- PFAS with an overhead anchor and verified clearance. Move the anchor above the D-ring so free fall is reduced, recalculate clearance, and check swing-fall hazards. A 6 ft lanyard anchored at shoulder height is not adequate here.
- Controlled access zone alone is not acceptable. A CAZ limits access but does not arrest a fall, so it does not protect a worker who can fall 12 ft to the footing.
Any PFAS selection must include inspection, training, 100% tie-off, and a rescue plan. The guardrail option should be chosen first because it removes the fall hazard rather than relying on arrest.
3. What rescue and post-arrest considerations must be addressed before work starts?
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Before work starts, the employer must have a prompt rescue plan that does not rely on the fallen worker self-rescuing. Address:
- Suspension trauma: a worker hanging in a harness can lose consciousness quickly. Plan for rapid retrieval or assisted descent and treat any suspension as a medical emergency.
- Rescue method: provide a retrieval line, controlled descent device, or ladder access, and assign trained rescuers. Call 911 early if the worker cannot be retrieved promptly.
- Communication: maintain continuous contact with the worker and confirm rescue equipment is on site and inspected.
- Anchor and equipment: verify the anchor can support the arrest forces, inspect the lanyard and harness, and remove any equipment that has arrested a fall from service.
- Post-fall: do not let the worker return to work until medically cleared; investigate the fall and revise the plan.