Weir & River Structure Fabrication SWMS
This Safe Work Method Statement covers the fabrication, installation, modification and maintenance of structures in and adjacent to a weir, river, creek, channel or catchment — including fixed and adjustable weir gates, penstocks, trash screens and debris racks, fishways, flow-measurement structures
SWMS variants reference your state’s WHS legislation. Instant download after payment.
Weir and river structure work covers fabrication, installation, modification and maintenance of structures in and adjacent to a weir, river, creek, channel or catchment — fixed and adjustable weir gates, penstocks, trash screens and debris racks, fishways, flow-measurement structures, guide walls, walkways and access gantries, and the steel fabrication that goes with them. It runs from site establishment on a riverbank and temporary flow diversion or gate closure, through dewatering, rigging and placement of fabricated components, in-stream and over-water welding and bolting, corrosion protection, and commissioning of the gate or screen through its full range of movement.
Water dominates every hazard on this job, and it does so in a way that is not intuitive. A weir concentrates flow into a smooth, fast, deceptively quiet chute above the crest and into a violent recirculating hydraulic below it. A person who enters that recirculation downstream of a weir is very unlikely to self-rescue — regardless of swimming ability, and regardless of a lifejacket. This is why drowning at low-head weirs kills strong swimmers and trained rescuers. The controls therefore treat the water as a place people are kept out of, rather than a place people are protected within.
The second thing that separates this work from ordinary civil construction is that water level is the one hazard the crew cannot control. Rainfall in a catchment tens of kilometres upstream can raise the level and velocity at the work face hours later, under a clear sky, with no visible warning at the site. Catchment weather monitoring and a defined trigger level with an unconditional evacuation rule are primary controls here, not contingency planning.
Underneath that sit confined space entry to gate chambers, valve pits, culverts, penstocks and fishways; falls from the crest, guide walls and gantries; and stored energy in a gate or penstock that can move while people are inside or below the structure.
Work adjacent to water with a risk of drowning, falls over 2 metres, confined space entry and powered mobile plant all make this high risk construction work under section 291, and a Safe Work Method Statement is required under section 299.
Hazards identified
14 hazards covered, sorted by priority.
Fatal drowning; the hydraulic below a low-head weir traps and recirculates a person and self-rescue is very unlikely even for strong swimmers
Workers and plant trapped or swept away; the rise arrives hours after rain the crew never saw and often under clear sky at the site
Fatal oxygen deficiency or hydrogen sulphide exposure; confined spaces at water structures accumulate gas from decomposing organic matter
Fatal impact injury, or a fall into water that immediately becomes a drowning event
Crushing, or sudden release of impounded water into the dewatered work area
Workers in a dewatered chamber inundated with no escape route; a failure gives no useful warning
Fatal crush injury; components are heavy, awkward and landed in constrained positions over water
Operator drowned in an overturned machine; saturated bank material fails without warning
Metal fume fever and respiratory disease; electric shock risk is elevated by wet conditions and conductive surroundings
Leptospirosis, gastrointestinal illness and cyanobacterial toxicity; rivers downstream of agriculture routinely carry all three
A swimmer, paddler or angler entering an area with altered flow or an operating gate
Acute lumbar and shoulder injury; loads are handled on unstable, sloping and slippery surfaces
Envenomation, with an evacuation time measured in hours at a remote river location
A survivable injury becomes fatal because definitive care is hours away and no one can call for it
Control measures
Hierarchy-of-controls order: elimination → substitution → isolation → engineering → administrative → PPE.
- 1Keep workers out of the water rather than protecting them in it: eliminate in-water work by dewatering, gate closure or flow diversion wherever it is achievable.
- 2Treat the recirculating hydraulic below the weir crest as an exclusion zone under all conditions, and never plan work, access or rescue that requires a person to enter it.
- 3Monitor catchment rainfall and upstream gauge data daily and before every shift, and set a defined water level and velocity trigger before work starts.
- 4Evacuate unconditionally on the trigger being reached, with no override available to any person on site, and recover plant only when it is safe to do so.
- 5Provide edge protection to all crest, guide wall, walkway and gantry work areas, using fall arrest only where edge protection is not reasonably practicable.
- 6Provide inherently buoyant lifejackets to AS 4758 for all work over or adjacent to water, and treat them as a last resort rather than a means of permitting in-water work.
- 7Position throw bags, rescue lines and a crewed rescue craft downstream, and rehearse the rescue plan before work commences.
- 8Enter any gate chamber, valve pit, culvert, penstock or fishway only under a confined space entry permit to AS 2865, with atmospheric testing, continuous monitoring, forced ventilation and a stand-by person.
- 9Isolate, physically restrain and lock out every gate, penstock and actuator, and prove zero energy, before any person enters or works below the structure.
- 10Design temporary flow diversion and coffer dams to an engineer's specification for the design flow, and inspect them before every shift and after every rainfall event.
- 11Maintain a defined escape route from every dewatered work area and confirm each worker knows it before entry.
- 12Assess and, where required, batter or matt the riverbank before plant access, and keep plant a defined distance from the bank crest.
- 13Provide local exhaust ventilation or respiratory protection for in-situ welding, and use a voltage-reduction device where welding in wet conditions.
- 14Provide potable washing water, cover all cuts and abrasions, prohibit eating without washing, and brief the crew on leptospirosis and blue-green algae symptoms.
- 15Notify the water authority, landholders and downstream users, and sign and physically control public access to the affected reach.
- 16Confirm satellite or HF communications, nominate an evacuation point and helicopter landing area, and provide a first aider with remote-appropriate capability before mobilising.
Applicable Codes of Practice
Governs entry to gate chambers, valve pits, culverts, penstocks and fishways, including permits, testing, ventilation and stand-by arrangements.
Governs edge protection at the weir crest, guide walls, walkways and gantries, and the preference for fall prevention over arrest.
Sets the framework for SWMS preparation and high risk construction work involving water, falls, confined spaces and powered mobile plant.
Applies to riverbank excavation, coffer dam construction and the assessment of saturated and sloping bank material.
Applies to in-situ welding on a wet structure, including fume control, arc flash and the elevated electric shock risk in conductive surroundings.
The technical standards for confined space entry procedure, and for inherently buoyant lifejacket selection for work over water.
Governs harness, lanyard and anchorage selection where fall arrest is used on crest, gantry and over-water work.
High-Risk Construction Work triggered
Engaged on essentially every task in this scope — the structure is in or beside the watercourse and the weir pool and downstream hydraulic are present throughout.
Engaged where work occurs on a weir crest, guide wall, walkway or access gantry above the pool, apron or rock — routine on weir structures.
Engaged where entry is made to a gate chamber, valve pit, culvert, penstock or fishway. Water structures accumulate gas from decomposing organic matter and are among the most dangerous confined spaces in civil work.
Engaged wherever a crane, excavator or telehandler operates on the riverbank for rigging, placement or dewatering.
Where any of these categories applies, the work is high risk construction work under section 291 of the Work Health and Safety Regulation and a Safe Work Method Statement must be prepared before the work commences under section 299. Where the work involves diving, Part 4.8 of the Regulation applies additionally and imposes its own duties. Confined space entry engages Part 4.3 independently of section 291, including the entry permit, atmospheric testing and stand-by person requirements. The SWMS must be reviewed under section 302 whenever the flow diversion arrangement changes, the water level trigger is reached, or an incident occurs.
Who this is for
- →Civil and water-infrastructure contractors constructing and maintaining weirs, gates and screens
- →Steel fabricators and welders working in-stream and over water on gates, penstocks and fishways
- →Water authorities, irrigation corporations and councils maintaining weirs and flow structures
- →Confined space and dewatering contractors entering gate chambers, culverts and penstocks
- →Environmental and fishway contractors installing flow-measurement and fish passage structures
What you receive
- ✓Editable Microsoft Word (.docx) document delivered as an instant download.
- ✓Sixteen identified hazards, each with an initial risk rating, a full control set written to the hierarchy of control, a residual rating and a nominated responsible person.
- ✓Regulatory reference bullets citing the governing sections verbatim, including the confined space and falls Parts and the diving work provisions.
- ✓A completed risk matrix using 5×5 likelihood × consequence scoring with both initial and residual ratings.
- ✓A PPE matrix mapping each task to the required protective equipment and the actual AS/NZS standard it must comply with, including lifejackets to AS 4758.
- ✓Emergency response provisions covering a person in the water, rapid water level rise, confined space rescue, coffer dam failure and remote evacuation.
- ✓The notifiable incident duty with the regulator's notification number.
- ✓A worker sign-on register for recording that each person has read and understood the statement before starting.
- ✓Fully editable text so your PCBU details, site address, personnel, plant and site-specific controls can be inserted.
- ✓State-specific variants available for all eight Australian jurisdictions with the correct Act, Regulation and regulator for each.
Worked example
A crew replaces a corroded trash screen and rebuilds the guide walls at a low-head weir on a regulated river. The gate is closed, the reach is dewatered behind a coffer dam, and the screen frame is lifted in by a 25 t crane sitting on a matted bank pad. The morning of day three is clear and still at the site. The upstream gauge tells a different story: 40 mm fell overnight in the headwaters, 60 km away, and the gauge is climbing. Nobody at the weir saw a drop of rain. The pre-shift check reads the gauge, compares it against the trigger level set in the SWMS, and the supervisor calls the evacuation before anyone enters the dewatered chamber. There is no debate about it — the rule is unconditional precisely so that the call is not a judgement made under pressure by someone who wants to finish the pour. The rise reaches the site six hours later and overtops the coffer dam. Everyone is on the bank watching it. Two other decisions on that job are worth stating. The gate chamber entry is treated as a full confined space permit — tested, continuously monitored, force ventilated, with a stand-by person on the hatch — because organic matter decomposing in a river structure generates hydrogen sulphide and strips oxygen, and the chamber had been closed for two years. Testing found 16% oxygen on first entry. And the rescue plan explicitly does not include anyone entering the water below the crest. The throw bags and the crewed craft are positioned downstream of the hydraulic, not in it, because a rescuer who enters the recirculation below a low-head weir becomes the second casualty. That has happened often enough in Australia that the plan is written to make it impossible rather than to make it brave.
Related legislation
- Work Health and Safety Act 2011 (NSW) — section 19 primary duty of care, section 47 consultation, sections 35–38 notifiable incidents
- Work Health and Safety Regulation 2025 (NSW) — section 291 high risk construction work, section 299 SWMS required, section 302 review
- Work Health and Safety Regulation 2025 (NSW) — Part 4.3 Confined spaces, Part 4.4 Managing the risk of falls, Part 4.8 Diving work
- Work Health and Safety Regulation 2025 (NSW) — Chapter 5 Plant, covering cranes, excavators and the gate actuators as plant
- AS 2865 Confined spaces, AS 4758 Lifejackets and AS/NZS 1891.1 Industrial fall-arrest systems
- Water Management Act 2000 (NSW) and the relevant water authority's approval conditions for works in a watercourse
Frequently asked questions
We'll all be wearing lifejackets — isn't that enough for the drowning risk?
No, and treating it as enough is how people die at weirs. A lifejacket keeps you afloat; it does not get you out of the recirculating hydraulic below a low-head weir, which holds a person against the face of the structure and recirculates them regardless of buoyancy. Lifejackets to AS 4758 are required, but they are the last line, not the control. The controls are elimination of in-water work by dewatering or diversion, edge protection, and an absolute exclusion zone on the hydraulic.
How do we manage a water level rise when the weather at the site is fine?
By monitoring the catchment, not the sky above you. The controls require daily and pre-shift review of upstream gauge and catchment rainfall data, with a defined water level and velocity trigger set before work starts. When the trigger is reached the evacuation is unconditional and no one on site can override it — because a rise from rain 60 km upstream arrives hours later under clear sky, and the person who wants to finish the task is the worst person to be making that call.
Do gate chambers and culverts really need a confined space permit?
Yes, and they are among the most dangerous confined spaces in civil work. Decomposing organic matter in a water structure consumes oxygen and generates hydrogen sulphide, so a chamber that has been closed for months can be immediately fatal on entry. Every entry requires a permit under AS 2865 with atmospheric testing, continuous monitoring, forced ventilation, a stand-by person and a rescue plan that does not require the stand-by person to enter.
Does this cover diving work?
The document identifies diving as conditional and flags the Part 4.8 duties, but it is not a diving SWMS. Where any part of the work requires a diver, Part 4.8 of the Regulation applies in addition, with its own competency, supervision, plant and dive plan requirements, and a dedicated diving SWMS is needed. Most of the scope is written to eliminate diving by dewatering or diversion.
What about the public and landholders?
This is a real and frequently underestimated risk on river work. Swimmers, paddlers and anglers use these reaches, and a gate operation or diversion changes flow conditions downstream of where the crew can see. The controls require notification of the water authority, landholders and downstream users, plus signage and physical control of access to the affected reach — not just the work area.
Which states does this cover?
All eight Australian jurisdictions. The NSW version cites the Work Health and Safety Act 2011 (NSW) and Work Health and Safety Regulation 2025 (NSW) with SafeWork NSW as the regulator. Each state variant carries the correct Act, Regulation and regulator. Note that works in a watercourse also require approval under state water legislation, which differs by jurisdiction and is outside the scope of the SWMS.