Diaphragm Wall Construction SWMS
SWMS variants reference your state’s WHS legislation. Instant download after payment.
The defining fact of diaphragm walling is that the excavation's support is a liquid. Nobody enters the trench — a d-wall panel is dug, reinforced and concreted entirely from the surface — and the ground is held open not by shields or shoring but by the hydrostatic head of the slurry standing in it. The slurry level IS the structural support: if it drops — a circulation failure, a loss into a gravel seam, a burst line, a tide the design did not allow for — the panel's walls become unsupported ground, and collapse can be sudden, can undermine the guide walls and the crane standing beside them, and can arrive with adjacent structures attached. Slurry level and density are watched like structural instrumentation, minimum head above groundwater is held at all times including overnight, and a falling level is an emergency, not a maintenance item.
The second defining hazard is the open trench itself. A slurry-filled panel is a deep body of dense liquid with vertical sides, and a person who goes in does not swim in it — bentonite offers nothing to swim against and everything to sink into. The trench is treated as a drowning hazard of the first order: covered or barriered except at the immediate working panel, never approached alone, never crossed or straddled. Around it operate some of the heaviest suspended loads in construction — grabs and kelly bars of many tonnes cycling all day, and reinforcement cages that are long, flexible and famous for buckling during the tilt from horizontal to vertical if lifted anywhere but the designed points. This SWMS covers guide wall construction, grab or hydromill excavation under bentonite or polymer slurry, slurry management, stop-end handling, cage tilt-up and tremie concreting. Authored for New South Wales. Regulator: SafeWork NSW.
Hazards identified
14 hazards covered, sorted by priority.
Sudden ground collapse when the level, the trench's only support, drops
A person who enters dense bentonite slurry does not come back up unaided
A long flexible cage folds and sheds bars over everyone below
Tools cycling hundreds of times a shift need to miss only once
The heaviest plant on site overturns into the deepest trench
Electrocution, gas release or flooding from a struck underground service
Electrocution or structural contact at full mast and boom height
Extraction loads exceed placement loads and arrive suddenly when the element breaks free
Slurry mixed into the wall becomes a permanent defect, and a slicked edge doubles the drowning hazard
A slurry line under pump pressure whips and blinds; cement burns the skin
The ordinary excavation that gets none of the deep trench's attention
Permanent hearing loss from sustained plant noise
A slip toward the open trench is the drowning hazard's opening move
Musculoskeletal injury, worsened by handling at the trench edge
Control measures
Hierarchy-of-controls order: elimination → substitution → isolation → engineering → administrative → PPE.
- 1Maintain slurry level and density within the engineer's stated limits at all times including overnight and weekends — the excavation's support is a liquid and the level IS the structure — with minimum head above groundwater per the design, reserve slurry batched and available, continuous level monitoring with alarms at the working panel, and density, viscosity and sand-content testing at the design frequency.
- 2Treat a falling level as an emergency, not a top-up — plant back from the panel, exclusion widened, reserve slurry committed — report losses into permeable seams to the geotechnical engineer before excavation resumes, and never leave a panel at reduced head.
- 3Cover or barrier the trench everywhere except the immediate working panel, limit the open length to what the operation needs, allow no person to cross, straddle or reach over the open trench, permit no work alone at the open panel, and keep a throw line, reach pole and retrieval point at the working panel.
- 4Lift reinforcement cages only by the designed lifting points to the documented tilt-up method, with engineered spreaders or a strongback, tandem or dual-hook tilt where the design requires, rated gear to AS 4991, and a full exclusion under the cage and its path for the whole lift and lower.
- 5Exclude all persons from the slew and travel path of the grab, kelly bar and hydromill for the whole excavation cycle, establish and barrier the rig's operating radius, and inspect hoses and ropes on the rig's schedule because a parted rope releases the grab.
- 6Stand the rig and crane on a designed and certified working platform assessed for the actual bearing pressures, inspect it after rain, slurry spills and any panel loss, and stop work on any settlement, cracking or slurry boiling at the surface.
- 7Locate every underground service before guide wall or panel excavation — plans obtained, a competent locator's marks on the ground, potholing by non-destructive means — and relocate, isolate or protect services in conflict under the asset owner's direction before excavation.
- 8Assess the plant's working envelope at full mast and boom height including cage tilt-up arcs, have the supply authority de-energise or relocate lines within that envelope or establish exclusion zones the mast and boom cannot enter, and hold approach distances to Part 4.7 with physical markers and a spotter.
- 9Maintain tremie embedment in the rising concrete per the method, plan concrete supply continuity so the pour never stalls, pipe displaced slurry back to the plant with surge capacity, and keep the edge zone from flooding — a slurry-slicked edge beside an open panel is the drowning hazard doubled.
- 10Operate the slurry plant to its documented procedure with lines depressurised before any break-in, fit whip-checks and guards, and handle bentonite, polymer and cement to the safety data sheets with dust controlled at the hopper and alkaline burns flushed immediately.
- 11Construct guide walls to the engineer's design with the shallow excavation battered or supported per the Excavation Code, apply silica and noise controls at breaking, and provide edge protection or covers at the open guide wall trench.
- 12Contain slurry at the panel and returns, squeegee and grit spills immediately, grade and drain the working platforms, and clean edge zones as a priority because the whole job runs on a liquid that turns every surface it touches into glass.
- 13Ensure all workers hold a current White Card (CPCCWHS1001), with the rig, crane and slurry plant operated only by competent and appropriately licensed persons and the dogger holding a high risk work licence class DG.
- 14Consult workers on WHS matters affecting them under Section 47 of the WHS Act 2011 (NSW), record the consultation, and review the SWMS under Section 302 whenever the ground, slurry design, plant, method or services change, after any incident, and at minimum every 12 months.
Applicable Codes of Practice
The benchmark for ground assessment, support, services and the zone of influence around the trench, applying to the panel, the guide walls and the ground the plant stands on.
The benchmark for the rigs, cranes, pumps and slurry plant — guarding, isolation, inspection and safe use of the powered plant that constitutes most of the work.
The benchmark for bentonite, polymers, cement and admixtures, including dust control at the hopper and alkaline burns from cement contact.
The design and installation benchmark for embedded retaining elements constructed under support fluid, including the slurry support requirements the head is maintained against.
The structural concrete requirements the tremie placement must achieve, and the basis of the mix's flow and setting behaviour during the pour.
The rated lifting gear for reinforcement cage, stop-end and tremie handling — the suspended loads that dominate the work.
High-Risk Construction Work triggered
A diaphragm wall panel is a deep excavation many metres below the surface, and the guide wall trench and panel are both excavation work managed for ground collapse.
The open panel is a deep trench full of dense bentonite or polymer slurry with vertical sides that a person cannot swim in, and a fall or entry is a drowning event.
Grabs, kelly bars, hydromills, cranes and slurry plant operate continuously at the trench, with multi-tonne tools and suspended cages cycling over the workface all shift.
Masts, crane booms and cages reach toward overhead lines at full height, and panel and guide wall excavation passes through a corridor of underground electrical services treated as live until proven otherwise.
Diaphragm wall construction is high risk construction work under Section 291 of the WHS Regulation 2025 (NSW) on multiple counts, so a SWMS must be prepared before work commences (Section 299), kept readily accessible, followed, and reviewed as necessary (Section 302), and given to the principal contractor if one is appointed. Part 4.3 Division 3 imposes the duty to manage excavation risks including ground collapse at the panel, the guide walls and the ground the plant stands on. Energised electrical work is separately prohibited under Part 4.7 Division 4, sections 154 and 157, unless de-energisation is not reasonably practicable. A panel collapse, a person in the slurry, a services strike, a load drop or any incident requiring immediate hospital treatment is a notifiable incident under Sections 35–38 of the WHS Act 2011 (NSW) — a dangerous incident is notifiable even where nobody is injured — and serious breaches are prosecuted as Category 1 or Category 2 offences, with the most serious carrying imprisonment for individuals. A slurry or concrete discharge to stormwater or waters is separately an offence under the POEO Act 1997 (NSW).
Who this is for
- →Geotechnical and piling contractors constructing diaphragm (slurry) walls by grab or hydromill under bentonite or polymer support.
- →Civil and basement contractors installing deep retaining and cut-off walls on constrained urban and infrastructure sites.
- →Principal contractors coordinating d-wall rigs, cranes, slurry plant and adjacent structures at the site boundary.
- →Geotechnical and temporary works engineers setting slurry design parameters, minimum head, guide wall design and the zone of influence.
- →WHS managers and HSE advisors responsible for excavation, drowning, lifting and services risk on deep foundation works.
What you receive
- ✓A complete, editable Safe Work Method Statement authored for New South Wales — the WHS Act 2011 (NSW), the WHS Regulation 2025 (NSW) and SafeWork NSW as regulator.
- ✓An 11-row document control table with editable fields for trade, document slug, version, dates, jurisdiction, prepared by, reviewed by, approved by, site and PCBU.
- ✓A detailed activity scope that names the real method — guide walls, grab or hydromill excavation under bentonite or polymer slurry, slurry batching and level management, stop-end handling, cage tilt-up and tremie concreting.
- ✓14 identified hazards with initial and residual risk ratings on a printed 5x5 matrix, each with controls ordered through the full hierarchy — eliminate, engineer, administrative, PPE.
- ✓The slurry-head control set built on the fact that the level IS the structure — minimum head above groundwater, reserve slurry, continuous monitoring and testing, and a falling level treated as an emergency rather than a top-up.
- ✓The drowning control set at the open slurry trench — cover or barrier except at the working panel, no crossing or reaching over, edge rescue by throw line and reach pole, and life jacket for edge-exposed tasks.
- ✓The lifting control set — cage tilt-up by the designed points, grab and kelly exclusion, stop-end and tremie handling, and a certified working platform under the plant — mapped to rated gear.
- ✓A regulatory references section citing Sections 291, 299 and 302, Part 4.3 excavation, AS 2159, AS 3600 and the Excavation, Plant and Hazardous Chemicals Codes; a PPE matrix mapping each task to its Australian Standard; emergency procedures including in-slurry rescue and the notifiable-incident duty; and a 12-row worker sign-on table.
- ✓Microsoft Word (.docx) format, unbranded, with editable fields for PCBU, ABN, site, prepared by, reviewed by, approved by and review date.
Worked example
A d-wall gang is constructing a basement cut-off wall on a constrained Sydney site, beside a live road and a heritage terrace. Mid-afternoon the grab breaks into a gravel seam and the slurry level in the open panel starts to fall — a steady drop becomes obvious at the guide wall. The temptation is to read it as a top-up: send someone to the plant, run more bentonite in, keep digging. This SWMS forbids exactly that. The slurry level is the panel's only support, and a seam swallowing slurry means unsupported ground is forming behind the guide wall — with the rig and crane standing right beside it. The procedure is to pull the plant back from the panel, widen the exclusion, commit the reserve slurry already batched for this reason, and report the loss to the geotechnical engineer before any excavation resumes, because a panel bleeding into a permeable seam can undermine the guide walls, the plant and the terrace footings together, and it can do it in minutes. Nobody approaches the edge to look. The reserve slurry, the alarms, the certified working platform and the engineer's authority to resume are not paperwork — they are the difference between a logged loss and a collapse that takes the footpath with it.
Related legislation
- Work Health and Safety Act 2011 (NSW) — Section 19 primary duty of care, extending to adjacent properties and the public at the site boundary; Section 47 consultation; Sections 35–38 notifiable incidents.
- Work Health and Safety Regulation 2025 (NSW) — Section 291 (high risk construction work) and Section 299 (preparation and content of a SWMS), with review under Section 302.
- Work Health and Safety Regulation 2025 (NSW) — Part 4.3 Division 3 (excavation work), managing ground collapse at the panel, the guide walls and the ground the plant stands on.
- Work Health and Safety Regulation 2025 (NSW) — Part 4.7 (electrical), including the prohibition on energised work at Division 4, sections 154 and 157, applying to overhead lines and struck underground electrical services.
- AS 2159 (Piling: Design and installation), AS 3600 (Concrete structures) and AS 4991 (Lifting devices), with the Excavation, Plant and Hazardous Chemicals Codes of Practice.
Frequently asked questions
Does buying this SWMS make our diaphragm wall work compliant?
No. This is a documentation set — a professionally authored, editable template — not compliance in itself. Compliance is what you do: the SWMS must be completed for your actual site, slurry design and plant, consulted on with the workers doing the job under Section 47, kept accessible on site, followed in practice, and reviewed under Section 302 whenever conditions change. A SWMS in a drawer that nobody worked to has never protected anyone. What you get is a rigorous, NSW-correct starting point that reflects how d-wall work actually fails — it does not replace the engineer's slurry design, the geotechnical assessment or the on-site supervision that keep the panel standing.
Why is a slurry trench treated as a drowning hazard when it isn't water?
Because bentonite slurry is denser than water and offers nothing to swim against — a person who goes in sinks rather than floats and cannot self-rescue, and a would-be rescuer who enters becomes a second casualty. That is why the WHS Regulation counts a slurry-filled trench as work in or near a liquid involving a risk of drowning under Section 291, why the trench is covered or barriered except at the working panel, and why rescue is by throw line and reach equipment from the edge — never by entry.
We monitor the slurry level carefully — why treat a small drop as an emergency?
Because the slurry level is not a consumable being topped up — it is the structure holding the trench open. A drop means the head above groundwater is falling and the walls are moving toward unsupported ground, and a loss into a gravel seam can accelerate without warning and undermine the guide walls and the plant beside them. Treating it as an emergency — plant back, exclusion widened, reserve slurry in, engineer informed before resuming — is the control that keeps a monitored loss from becoming a collapse. A level watched like structural instrumentation is watched for exactly this moment.
Is this ready to use, or do we have to fill things in?
It ships as an editable Word document with fields for your PCBU, ABN, site, personnel and review date, and it is written to be completed, not signed blank. The slurry design parameters, minimum head, guide wall design, working platform certification and services information are site-specific inputs your geotechnical and temporary works engineer must supply — this SWMS is structured to receive them and to make their absence obvious, so a panel is never dug against blanks.