Hydrodemolition — Safe Work Method Statement
Safe Work Method Statement for removing concrete with ultra-high-pressure water using a remote-controlled hydrodemolition robot or handheld lance, covering set-up, structural checks, operation, slurry management and clean-up.
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Hydrodemolition removes deteriorated or sound concrete with water jets at pressures that can exceed 1000 bar, leaving reinforcement intact for concrete repair on bridges, car parks, wharves and slabs. The water jet will cut through skin, muscle and bone, and injection injuries can be fatal hours later. Hydrodemolition is High Risk Construction Work where it removes concrete that forms part of the load path, because removing cover and concrete around reinforcement can affect the structure's integrity and may require temporary propping. Powered mobile plant (the robot and the power pack truck) is also moving, and work on car park decks, bridges or wharves often involves a fall risk of more than 2 metres.
Robot operation is preferred over handheld lancing. The operator stays outside the jet's range with the remote, and the work area is fully enclosed. Handheld lancing at these pressures carries a much higher risk and should be limited to small areas the robot cannot reach. AS/NZS 4233.1 sets requirements for the safe operation of high-pressure water jetting systems, including hydrodemolition, and operators must be trained and competent to it.
Other task-specific hazards include flying concrete and steel fragments that can travel well beyond the immediate work area, noise often well over 100 dB(A), high-pH slurry that burns skin and is a pollutant, embedded electrical conduits and post-tensioning tendons, and water getting into floors below. Before starting, an engineer should define the removal depth and area and confirm whether propping is needed.
Slurry from hydrodemolition is highly alkaline and contains fine concrete particles. It must be collected, settled and pH-adjusted before any discharge, and discharge to sewer or stormwater usually needs approval from the water authority or local council.
Customise this template with the structure and elements being treated, the engineer's removal specification and propping design, the pump pressure and flow, the robot and lance equipment, the exclusion zone and screening layout, embedded services and tendons located, the slurry treatment and discharge approval, and the noise management plan.
Personal Protective Equipment
High Risk Construction Work Types
- •Risk of a person falling more than 2 metres
- •Demolition of an element of a structure that is load-bearing or related to its physical integrity
- •Structural alterations or repairs that require temporary support to prevent collapse
- •Work in an area with movement of powered mobile plant
Risk Assessment
1.Engineering review and service location
| Hazard / Risk | Initial Risk | Control Measures | Residual Risk | Responsibility |
|---|---|---|---|---|
| Removal weakens the structure | Catastrophic | Engineer specifies removal depth, area and sequence and any propping. Props installed and checked before removal starts. Removal stops if unexpected cracking, deflection or exposed tendons are found. | Low | Engineer / Supervisor |
| Jet cuts live conduits or post-tensioning tendons | Catastrophic | Scan the slab to locate conduits and tendons. Isolate embedded electrical circuits. Mark no-go areas and set robot limits around them. | Low | Supervisor / Licensed Electrician |
2.Set-up of pump unit, hoses and work area
| Hazard / Risk | Initial Risk | Control Measures | Residual Risk | Responsibility |
|---|---|---|---|---|
| Hose or fitting failure under ultra-high pressure | High | Use hoses and fittings rated above pump maximum pressure. Inspect daily and replace damaged hoses. Whip checks on all connections. Hose runs protected from plant and kept out of walkways. | Low | Pump Operator |
| Flying debris leaves the work area | High | Enclose the work area with screens or barriers that contain rebound. Exclusion zone sized for the pressure and set-up and marked with signage. Protect openings, edges and soffits below. | Low | Supervisor |
| Fall from edge of deck or bridge | Catastrophic | Edge protection in place at all open edges and penetrations before work starts. | Low | Supervisor |
3.Robot hydrodemolition
| Hazard / Risk | Initial Risk | Control Measures | Residual Risk | Responsibility |
|---|---|---|---|---|
| Jet strikes a person | Catastrophic | Operator stays outside the robot's reach and jet trajectory. Nobody enters the exclusion zone while the jet is on. Pump and robot have emergency stops; the remote has a dead-man function tested at start-up. | Low | Robot Operator |
| Robot tips or falls through weakened deck | High | Engineer confirms deck can carry the robot. Robot kept on sound concrete away from edges and openings. | Low | Robot Operator / Engineer |
| Noise-induced hearing loss | High | Double hearing protection for crew inside the zone. Pump unit placed away from occupied areas. Comply with permitted work hours. | Low | All Workers |
4.Handheld lancing in areas the robot cannot reach
| Hazard / Risk | Initial Risk | Control Measures | Residual Risk | Responsibility |
|---|---|---|---|---|
| Water jet injection injury to lance operator | Catastrophic | Handheld lancing only by operators trained to AS/NZS 4233.1. Lance fitted with dead-man trigger and correct length. Two-person team with the pump operator in line of sight. Pressure set to the lowest effective level. Any jet injury treated as a medical emergency; operator carries a medical alert card describing water injection injury. | Moderate | Lance Operator / Pump Operator |
| Fatigue and loss of control from jet reaction force | High | Limit lancing time and rotate operators. Use a shoulder stock or lance support where available. | Moderate | Supervisor |
5.Slurry and water management
| Hazard / Risk | Initial Risk | Control Measures | Residual Risk | Responsibility |
|---|---|---|---|---|
| Alkaline slurry burns to skin and eyes | Moderate | Waterproof clothing and chemical gloves. Eye wash on site. Wash skin contact immediately. | Low | All Workers |
| Slurry enters stormwater or leaks to areas below | High | Seal drains. Collect slurry with vacuum truck or bunded sump. Settle and adjust pH before discharge under the approval. Protect floors and vehicles below from water leaking through the slab. | Low | Supervisor |
6.Clean-up and handover
| Hazard / Risk | Initial Risk | Control Measures | Residual Risk | Responsibility |
|---|---|---|---|---|
| Slips and trips on wet, broken surfaces with exposed reinforcement | Moderate | Vacuum loose material. Mark or cover exposed bars. Restrict access until the area is ready for repair works. | Low | Crew |
| Stored pressure when disconnecting equipment | High | Shut down pump and bleed pressure to zero before disconnecting hoses or lance. | Low | Pump Operator |
Relevant Codes of Practice
Worker Acknowledgement
By signing below, I confirm that I have read, understood and agree to comply with this Safe Work Method Statement.