Deep Trench Plumbing Repair >1.5m SWMS
Safe work method statement for plumbing repair and installation in excavations exceeding 1.5m depth including shoring, benching, batter slopes, and emergency rescue planning under WHS Regulations.
SWMS variants reference your state’s WHS legislation. Instant download after payment.
Deep trench plumbing repair covers the excavation of deep trenches to access, repair or replace deep underground plumbing, drainage and sewer pipework — digging down to a deep pipe, working in the trench to make the repair, and backfilling. It is among the most hazardous plumbing excavation work because the depth multiplies the consequences of a trench collapse, which is a leading cause of excavation fatalities, and the deep trench is also a confined space with the biological and atmospheric hazards of the drainage being repaired. This document is written on the basis that deep trench repair is carried out with the trench rigorously supported against collapse, the confined-space and biological hazards controlled, and the excavation managed by a competent person.
Deep trench plumbing repair is carried out to the excavation Code of Practice, which requires the trench to be supported against collapse by benching, battering or shoring appropriate to the depth and ground, with existing services located first, and the deeper the trench the more critical the support. The trench is also a confined space, with atmospheric and biological hazards where the drainage is exposed, and the repair is carried out in connection with the relevant parts of AS/NZS 3500. This document coordinates the trench-support, confined-space, biological and services controls so the deep repair is carried out without a collapse or atmospheric incident.
Hazards identified
9 hazards covered, sorted by priority.
Burial and crush injury, frequently fatal, from collapse of the deep trench
Oxygen deficiency or contaminated atmosphere in the deep trench
Electrocution, gas release or service damage where services are not located
Infection from contact with sewage where drainage is exposed
Trench instability and working in water in the deep excavation
Delayed escape and rescue from the deep trench
Impact injury from spoil or materials falling into the deep trench
Musculoskeletal injury working in the confined trench position
Crush and run-over injury where plant and workers are not separated
Control measures
Hierarchy-of-controls order: elimination → substitution → isolation → engineering → administrative → PPE.
- 1Engineering: support the deep trench against collapse by benching, battering or shoring appropriate to the depth and ground, designed by a competent person, recognising that the deeper the trench the more critical the support and that trench collapse is frequently fatal.
- 2Engineering: locate, prove and protect existing underground services before any ground penetration using plans, Dial Before You Dig information, a service locator and potholing, so services are not struck.
- 3Administrative: apply the confined space entry permit, atmospheric testing, ventilation, standby and rescue controls to the deep trench where it meets the confined space definition, with a SWMS for the excavation high risk construction work.
- 4Administrative: manage the biological hazard from the exposed drainage with hygiene controls, washing facilities and protective clothing, and prohibition of eating, drinking and smoking until decontaminated.
- 5Engineering: manage water ingress so it does not undermine the deep trench, and provide safe access and egress — a ladder or ramp — from the deep trench.
- 6Engineering: keep spoil and materials back from the trench edge and prevent them falling into the trench, and maintain plant-and-pedestrian separation with a spotter.
- 7Engineering: carry out the repair in connection with AS/NZS 3500, and backfill and reinstate the trench correctly.
- 8Administrative: ensure the work is carried out and certified by an appropriately licensed plumber or drainer under the relevant state or territory plumbing licensing scheme, with the relevant competencies and a compliance certificate issued where required.
- 9Administrative: all workers must hold a valid White Card (General Construction Induction Training, CPCCWHS1001) before entering any construction workplace, with the plumbing, excavation, confined space and any other competencies and licences required for the work.
- 10Administrative: conduct a daily pre-start toolbox talk covering the day's work, identified hazards, isolations, required PPE and emergency procedures, and record attendance in the consultation section.
- 11Administrative: consult workers and any health and safety representatives on the work and its risks, record the consultation, and keep this document available at the workplace.
- 12PPE: eye protection to AS/NZS 1337.1, hearing protection where required, gloves appropriate to the task, high-visibility clothing, and Class I or Class II safety footwear with protective toecap to AS/NZS 2210.3.
- 13Administrative: review and update this SWMS whenever the work scope changes, after any incident or near miss, when a worker or health and safety representative raises a concern, when new hazards are identified, or at minimum every 12 months.
Applicable Codes of Practice
Trenching and excavation controls including support against collapse, ground assessment and existing services.
Atmospheric testing, ventilation, entry permit and rescue controls where the work involves entry into a confined space.
The sanitary plumbing and drainage standard for the deep pipework being repaired.
The risk management process and hierarchy of controls applied to the hazards of the work.
Selection, fit testing and use of respiratory protection where dust, fumes or atmospheric hazards require it for the work.
High-Risk Construction Work triggered
A deep trench plumbing repair is, by definition, work in a trench deeper than 1.5 metres, which is high risk construction work requiring a SWMS before the work commences.
The deep trench can meet the confined space definition with an oxygen-deficient or contaminated atmosphere, which is high risk construction work requiring a SWMS before the work commences.
This is licensed plumbing, drainage or specialist work that, in the circumstances described, is high risk construction work — in or near a shaft or trench with an excavated depth greater than 1.5 metres; and in or near a confined space — so a SWMS must be prepared before the work commences, kept readily accessible, reviewed as necessary, and given to the principal contractor if one is appointed. The work is carried out to the relevant AS/NZS 3500 plumbing and drainage standards, the excavation, confined space and pressure-equipment requirements, and the relevant utility requirements, which are called up by the relevant legislation, with the excavation, confined-space, electrical, pressurised-pipe or work-at-height controls applied as relevant. A failure in this work can cause burial, an atmospheric incident, a service strike, a loss of containment or serious injury, and breaches of the relevant legislation and the primary duty of care under the model WHS Act are actively enforced, with offence categories running from failure-to-comply through to reckless conduct, and the most serious breaches carrying imprisonment for individuals. Body-corporate maxima are substantial and indexed; the current maximum follows the prevailing schedule of the responsible regulator.
Who this is for
- →Licensed plumbers and drainers carrying out deep trench repairs.
- →Civil and drainage contractors repairing deep pipework.
- →Plumbing businesses providing deep underground repair.
- →Asset owners and PCBUs requiring deep trench plumbing repair.
- →PCBU safety managers and supervisors coordinating the trench-support, confined-space and biological controls.
What you receive
- ✓Editable Microsoft Word document (.docx) fully compatible with Microsoft Word 2016 and newer, Google Docs, and LibreOffice Writer.
- ✓Title page with editable fields for PCBU name, ABN, site address, project name, principal contractor details, and document revision date.
- ✓Hazard register with the deep trench plumbing repair hazards — each with a documented consequence, inherent risk rating on a 5x5 likelihood-consequence matrix, hierarchy-of-control measures, and residual risk rating.
- ✓Deep trench repair prompts referencing the excavation Code of Practice and AS/NZS 3500, a trench-support and collapse-prevention section, a confined-space and atmospheric section, and a biological-hazard and access section.
- ✓Licensing, competency and permit prompts for the relevant plumbing, excavation, confined space and specialist work, and a respiratory protection selection and fit-test record per AS/NZS 1715 where relevant.
- ✓Worker consultation record per the model WHS Act consultation duty and a worker sign-on register (blank, expandable).
- ✓Applicable legislation and Codes of Practice schedule pre-populated for the model WHS jurisdiction with a state-variance reference table covering the harmonised states, plus Victoria.
- ✓Emergency procedure template and a revision log.
Worked example
A licensed drainer is engaged to repair a deep sewer pipe by deep trench excavation. Existing underground services are located, proved and protected before excavation. The deep trench is supported against collapse by shoring designed by a competent person appropriate to the depth and ground, recognising that trench collapse is frequently fatal and the deeper the trench the more critical the support, with a SWMS prepared for the excavation. The deep trench meets the confined space definition, so the confined space entry permit, atmospheric testing, ventilation, standby and rescue controls apply. The biological hazard from the exposed drainage is managed with hygiene controls, washing facilities and protective clothing. Water ingress is managed so it does not undermine the trench, and safe access and egress provided by a ladder. Spoil and materials are kept back from the trench edge, and plant-and-pedestrian separation maintained with a spotter. The repair is carried out in connection with AS/NZS 3500, and the trench backfilled and reinstated. The records are retained.
Related legislation
- Model Work Health and Safety Act — primary duty of care; the duty to consult workers; the reckless-conduct offence; and notifiable-incident provisions, as enacted in each jurisdiction.
- Model Work Health and Safety Regulations — Section 291 high risk construction work and the SWMS preparation and review duties, and the excavation, confined space and pressurised-pipe provisions where applicable, as enacted in each jurisdiction.
- The relevant plumbing and drainage standards AS/NZS 3500 (Parts 0–5), the excavation and confined space Codes of Practice, the pressure equipment and pipework standards, and the silica Code of Practice where cutting concrete, are called up by the relevant legislation, together with the Before You Dig Australia information and the relevant utility requirements.
- Plumbing and drainage work is licensed under each state and territory's plumbing licensing scheme, with the relevant competencies for excavation, confined space and specialist work, and compliance certification required for notifiable work; electrical work is carried out by a licensed electrician.
- Victoria operates under the Occupational Health and Safety Act 2004 and the Occupational Health and Safety Regulations 2017, with the high risk construction work, excavation and confined space provisions applying in place of the model instruments.
Frequently asked questions
Why is deep trench repair so hazardous?
Deep trench repair is among the most hazardous plumbing excavation work because the depth multiplies the consequences of a trench collapse, which is a leading cause of excavation fatalities. The deep trench is also a confined space with atmospheric and biological hazards where the drainage is exposed, so the trench support, confined-space and biological controls are critical.
How is the deep trench supported against collapse?
The deep trench is supported against collapse by benching, battering or shoring appropriate to the depth and ground, designed by a competent person, with the deeper the trench the more critical the support. Trench collapse is frequently fatal, so the support against collapse is the defining control for deep trench work, and a SWMS is prepared for the excavation.
Is a deep trench a confined space?
Yes, a deep trench can meet the confined space definition with an oxygen-deficient or contaminated atmosphere, particularly where drainage is exposed. The confined space entry permit, atmospheric testing, ventilation, standby and rescue controls apply, in addition to the trench support, and the work is high risk construction work requiring a SWMS.
What biological hazards apply?
The drainage being repaired exposes workers to sewage, which carries infection risk, so the biological hazard is managed with hygiene controls, washing facilities, protective clothing, and prohibition of eating, drinking and smoking until decontaminated. The biological hazard is managed alongside the trench-support and confined-space controls.
How is access and egress managed in a deep trench?
Safe access and egress — a ladder or ramp — is provided from the deep trench, so workers can escape and a rescue can be carried out. Because the deep trench multiplies the consequences of an incident and can be a confined space, safe access and egress and documented rescue arrangements are essential parts of the controls.