Controlled mechanical demolition of a two-storey reinforced concrete and masonry commercial building (~600m2 footprint) on a CBD site with shared boundary walls. Building has been cleared of all hazardous materials (asbestos removal completed under separate contract — clearance certificate obtained). Work involves top-down mechanical demolition using a 30-tonne excavator with hydraulic breaker and sorting grab, material segregation, crushing of concrete on site, and removal of debris.
This SWMS does not cover asbestos removal (completed separately), underpinning of adjacent buildings, or decontamination of any soil contamination discovered during works.
| Hazard | Inherent Risk | Control Measures | Residual Risk |
|---|---|---|---|
| Structural collapse Uncontrolled collapse of building elements during demolition — post-tensioned slabs, load-bearing walls, or destabilised structure sections |
4 x 5 = 20 Extreme |
Engineering Demolition sequence engineered by a structural engineer — approved demolition plan specifying order and method for each structural element Engineering Temporary propping installed where required by engineer before removing adjacent load-bearing elements Isolation Minimum 6m exclusion zone around active demolition face — no personnel within the zone during mechanical demolition Administrative Demolition supervisor to monitor structural condition continuously; cease work if unexpected movement or cracking observed |
2 x 5 = 10 High |
| Falling debris Concrete fragments, masonry, steel reinforcement, and demolition debris falling from upper levels to ground |
4 x 4 = 16 High |
Isolation Full-height hoarding around site perimeter with protective gantry over public footpath; exclusion zone enforced Engineering Catch platforms and debris netting on scaffolding where demolition face is near boundaries Administrative Top-down demolition sequence — material falls inward to building footprint, not outward PPE Hard hats, safety glasses, and steel-cap boots mandatory for all personnel on site |
2 x 4 = 8 Medium |
| Dust and silica exposure Respirable crystalline silica (RCS) generated by mechanical breaking of concrete; general demolition dust affecting workers and neighbouring properties |
4 x 4 = 16 High |
Engineering Continuous water suppression on all active demolition areas — mist cannons and hose sprays to keep dust below WES Engineering Dust monitoring equipment at site boundaries and downwind receptors; alert levels set at 50% of WES Administrative Cease breaking operations if visible dust escapes site boundary; increase water suppression before resuming PPE P2 respirators for all personnel on site; upgrade to powered air-purifying respirator (PAPR) for operators of concrete breakers |
2 x 4 = 8 Medium |
| Asbestos (unexpected finds) Despite prior removal, hidden asbestos-containing materials (ACM) may be encountered in walls, floors, or service ducts during demolition |
3 x 5 = 15 High |
Elimination Pre-demolition asbestos survey completed; all identified ACM removed by licensed contractor with clearance certificates Administrative Asbestos awareness training for all site personnel — ability to identify suspect materials and stop-work protocol Administrative If suspected ACM discovered: stop work immediately, isolate area, notify demolition supervisor, engage licensed assessor for sampling PPE P2 respirators worn during all demolition activities as precautionary measure |
1 x 5 = 5 Medium |
| Noise Sustained high noise levels from hydraulic breakers (up to 115 dBA), concrete crushing, and excavator operations exceeding 85 dBA TWA |
4 x 3 = 12 High |
Substitution Use hydraulic crushing attachment where possible instead of impact breaker — lower noise output Engineering Noise barriers (acoustic hoarding) on boundaries adjacent to occupied premises Administrative Restrict high-noise operations (breaking) to 8am-5pm weekdays per resource consent; noise monitoring at boundary PPE Class 5 hearing protection mandatory within 50m of active demolition |
2 x 3 = 6 Medium |
| Mobile plant interaction Multiple large machines (30T excavator, 10T loader, trucks) operating on congested CBD site; risk of striking workers |
3 x 5 = 15 High |
Isolation Designated pedestrian routes separated from plant operating areas by physical barriers; no-go zones marked Engineering All plant fitted with ROPS, FOPS, reversing cameras, proximity alarms, and flashing beacons Administrative Traffic management plan with dedicated traffic controller for all truck movements; radio communication between operators PPE High-visibility Class D/N garments (AS/NZS 4602) for all ground personnel |
2 x 5 = 10 High |
If an uncontrolled collapse occurs, all personnel to evacuate to the assembly point immediately. Account for all workers. Call 111 — request Fire and Emergency NZ Urban Search and Rescue if any person is trapped. Do not re-enter the site until a structural engineer has assessed stability. Notify WorkSafe NZ as a notifiable event.
Stop all work in the affected area immediately. Evacuate personnel upwind. Barricade the area. Do not disturb, sweep, or clean up the material. Contact a licensed asbestos assessor for sampling. Do not resume demolition in the area until clearance is obtained.
All workers must read and understand this SWMS before commencing work. By signing below, each worker confirms they have been briefed on the hazards, controls, and emergency procedures, and agree to follow them.
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