Safe Work Method Statement: Sewer Trenching and Underground Services (Depths to 2.1 m)
•PCBU / Company: Carraway Plumbing Pty Ltd
•Contact Person: Priya Nair
•Principal Contractor / Builder: Sandalford Estates Pty Ltd
•Site Address: 6 Pindan Way, Baldivis WA 6171
•Project Name: Baldivis Stage 3 Sewer Connections
•Work Activity Covered by this SWMS: Trenching and laying underground sewer services at depths up to 2.1 m, including services location, excavation, trench support, pipe laying, pit entry, backfill and testing
•Date Prepared: 18 August 2026
•Review Date: Review and revise this SWMS whenever the work, the hazards or the controls change, in accordance with reg 302 of the Work Health and Safety (General) Regulations 2022 (WA)
1. Work Activity & Scope
Carraway Plumbing Pty Ltd will excavate trenches and lay underground sewer services at 6 Pindan Way, Baldivis WA 6171 for principal contractor Sandalford Estates Pty Ltd, as part of the Baldivis Stage 3 Sewer Connections project. The sewer runs reach 2.1 m deep at the deepest connection points. The work runs from services location through excavation, trench support, pipe laying, pit connections and backfill to final testing.
The crew is 3 workers: a licensed plumber who supervises the work, a second plumber, and a plant operator. Planned duration is 8 days.
Parts of this activity are high risk construction work under reg 291 of the Work Health and Safety (General) Regulations 2022 (WA), so this SWMS was prepared before the work started as required by reg 299. A copy goes to Sandalford Estates Pty Ltd before work commences under reg 301, the work must be carried out in accordance with this SWMS or stop under reg 300, and the SWMS is kept until the high risk construction work is complete under reg 303.
2. High Risk Construction Work Categories
The following categories under reg 291 apply to this activity:
•Work in or near a trench deeper than 1.5 m: the sewer runs on this stage are excavated to 2.1 m at the connection points.
•Work in or near a confined space: the new maintenance shafts and connection pits are confined spaces once constructed, and the connection work requires workers to enter them.
•Work in an area with movement of powered mobile plant: an excavator digs the trench, shifts spoil and lowers pipe and shields while workers are on foot nearby.
The category applies to a trench deeper than 1.5 m, but the reg 306 support duty applies to any trench that is 1.5 m deep or deeper. The work method below applies trench support from 1.5 m.
3. Persons, Roles & Responsibilities
•Plumber-supervisor (Priya Nair): licensed plumber and site supervisor. Briefs this SWMS, holds the services information, directs the excavation sequence, inspects trench support daily and after rain, issues entry permits, and stops work if conditions change.
•Plumber 2: licensed plumber. Lays and joints the pipework, enters the trench only where support is in place, and enters a pit or shaft only under a current entry permit.
•Plant operator: operates the excavator, maintains the exclusion zone, never digs while anyone is in the trench, and takes direction from the spotter.
•Sandalford Estates Pty Ltd (principal contractor): receives this SWMS before work starts, coordinates other trades, and keeps them clear of the work area.
•All workers: hold a current general construction induction card (white card) under regs 316 and 317, sign on to this SWMS, report changed conditions, and may stop the work.
4. Plant, Equipment & Materials
•Excavator with a manufacturer-rated lifting point for pipe and shields
•Trench shields and hydraulic shoring sized for the trench depths
•Secured access ladders extending above the landing point
•Calibrated and bump-tested gas detector
•Forced ventilation blower and ducting
•Retrieval tripod, rescue winch, full-body harness and retrieval line
•Sewer pipe, fittings and bedding material
•Pipe laser and levels for grade control
•Barricading, mesh and signage
•First aid kit; the crew carries a charged phone
All plant and equipment is inspected before use. Defective items are tagged out and removed.
5. Step-by-Step Work Method: Hazards, Risk Ratings & Controls
Step 1: Underground services location and set-out
•Hazards: Striking buried electrical, gas, water or communications services; setting out the trench over services that were never located
•Initial risk: High (L3 x C5)
•Controls: Obtain current underground essential services information through a Before You Dig Australia enquiry before any excavation, brief the crew, and keep the plans on site, as required by reg 304. Treat every located electrical service as live. Prove the position and depth of each located service by hand digging (potholing) before the excavator works near it, and hand-dig within 300 mm of any located service. Mark proved services and the trench alignment before digging.
•Residual risk: Low (L1 x C4)
•Responsible: Plumber-supervisor
Step 2: Trench excavation with the excavator
•Hazards: Workers struck by the excavator or bucket; ground collapse; falls into the excavation; plant surcharging the walls
•Initial risk: High (L4 x C5)
•Controls: Manage the excavation risks, including ground collapse, under reg 305. No worker enters the exclusion zone covering the excavator's full slew radius while it digs, and no one is in the trench during excavation. A nominated spotter directs the operator from outside the slew radius. Plant and vehicles keep back from the trench edge. Barricade the excavation on all sides: a fall into the trench is liable to cause injury and is controlled under regs 78 and 79.
•Residual risk: Medium (L2 x C4)
•Responsible: Plant operator, plumber-supervisor
Step 3: Trench support installation and inspection
•Hazards: Trench wall collapse burying a worker; ground water softening the walls; plant vibration destabilising the excavation
•Initial risk: High (L4 x C5)
•Controls: Every part of the trench that is 1.5 m deep or deeper is shored, benched or battered before any person enters it, as required by reg 306; on this job that means shields or hydraulic shoring placed from the surface, as no written geotechnical advice permitting otherwise exists. Workers stay within the protection of the shield. A secured ladder stays inside the supported zone, within reach of the workers, and moves along with the work. Spoil sits at least 600 mm back from the trench edge. The plumber-supervisor inspects the trench and support each day, after rain, and after any event affecting stability, before anyone re-enters.
•Residual risk: Low (L2 x C3)
•Responsible: Plumber-supervisor
Step 4: Laying and jointing pipe in the trench
•Hazards: A suspended pipe or shield striking workers; crushed hands during placement; manual handling injuries; sewage contact at the tie-in
•Initial risk: High (L3 x C4)
•Controls: Pipes and shields are lowered by the excavator on the manufacturer-rated lifting point and slings; no worker stands under a suspended load, and workers in the trench stand clear until the load is at knee height inside the shield, guided by taglines. Bedding is screeded before each pipe is laid; jointing follows the pipe manufacturer's instructions. Two workers share each length. At the tie-in, workers wear gloves and eye protection, cover cuts, and wash before eating or drinking.
•Residual risk: Medium (L2 x C3)
•Responsible: Plumber 2, plant operator
Step 5: Confined space entry into connection pits and maintenance shafts
•Hazards: Oxygen deficiency; toxic atmosphere including hydrogen sulphide; flammable atmosphere; engulfment; difficult rescue
•Initial risk: High (L3 x C5)
•Controls: Pit and shaft entry is managed under the confined space duties in regs 62 to 77. A written risk assessment under reg 66 precedes any entry, and entry occurs only under a reg 67 permit issued by the plumber-supervisor. The atmosphere is tested before entry and monitored continuously; no one enters, and any entrant leaves at once, if readings fall outside the limits in the risk assessment. Forced ventilation runs before and during every entry. A trained standby person stays outside in continuous communication, with the tripod, winch and line rigged before entry. The standby person never enters; rescue is by retrieval from outside and by calling 000.
•Residual risk: Medium (L2 x C4)
•Responsible: Plumber-supervisor (permit issuer), Plumber 2 (entrant)
Step 6: Backfill and reinstatement
•Hazards: Workers in the trench during machine backfilling; collapse as support is removed; plant close to the open edge
•Initial risk: High (L3 x C4)
•Controls: No person is in the trench while the excavator places backfill. Support is removed progressively as the backfill rises, so no worker is ever in a part of the trench 1.5 m deep or deeper without support in place. Backfill is compacted in layers with marker tape above the pipe. Barricading stays up until each run is reinstated. The excavator exclusion zone applies as during excavation.
•Residual risk: Low (L1 x C3)
•Responsible: Plant operator, plumber-supervisor
Step 7: Testing the completed line
•Hazards: Stored energy released by a test plug failing or removed under pressure; re-entry into pits for test equipment
•Initial risk: Medium (L3 x C3)
•Controls: Use test equipment rated for the pressure, fitted to the manufacturer's instructions, and test from the surface wherever possible. No worker stands in front of a plug while the line is under test, and pressure is released fully before any plug is removed. Any re-entry into a pit requires a new permit under reg 67, with the full entry controls above.
•Residual risk: Low (L1 x C3)
•Responsible: Plumber-supervisor
6. Personal Protective Equipment
PPE supplements the controls above and is provided and used under the duties in regs 44 to 47:
•Hard hat, high-visibility clothing and steel-capped boots: at all times on site
•Gloves: handling pipe, shields and bedding, and all tie-in work
•Eye protection: cutting pipe, compacting, and tie-in work
•Hearing protection: near the excavator and compaction plant
•Full-body harness with retrieval line: every confined space entrant
•Sun protection: outdoor work for the full 8 days
All PPE is inspected before use and replaced if damaged.
7. Permits, Licences & Training Requirements
•The plumber-supervisor and the second plumber hold the plumbing licence classes required in Western Australia for sewer drainage work; details are recorded at induction.
•Every worker holds a current general construction induction card (white card) under regs 316 and 317.
•The plant operator is assessed as competent on the excavator, with records on site.
•Lifts use the excavator's manufacturer-rated lifting point with pre-slung loads; any dogger must hold the relevant high risk work licence under reg 81.
•Confined space entrants, standby persons and permit issuers are trained for those roles. Every entry runs under a reg 67 entry permit.
•The crew completes the Sandalford Estates Pty Ltd site induction before starting.
8. Emergency Procedures
•The address for emergency services is 6 Pindan Way, Baldivis WA 6171; call 000 in any emergency. The assembly point and nearest medical help are confirmed at the builder's induction.
•Trench collapse: call 000 at once, keep plant and workers off the ground near the collapse, and do not enter; the supervisor controls the scene until emergency services arrive.
•Confined space emergency: the standby person raises the alarm, calls 000, and retrieves the entrant from outside using the rigged tripod and winch, never by entering the space.
•Struck buried service: stop and move everyone clear, treat a struck cable as live, and call 000 and the asset owner's emergency number from the Before You Dig Australia plans before anything else moves.
•Injury or plant incident: make the area safe, call 000 if needed, give first aid. Incidents and near misses go to the plumber-supervisor and Sandalford Estates Pty Ltd; notifiable incidents go to WorkSafe WA with the scene preserved.
9. Monitoring, Review & Consultation
•The plumber-supervisor confirms compliance with this SWMS at each day's pre-start. Under reg 300, work that does not follow this SWMS stops until it complies or the SWMS is revised.
•This SWMS is reviewed and revised under reg 302 whenever ground conditions, depths, plant or services information change, and after any incident or near miss.
•The crew was consulted in preparing this SWMS and signs on below. Any worker can stop the job to raise a concern.
•A copy stays at the work area until the high risk construction work is complete under reg 303; a copy went to Sandalford Estates Pty Ltd under reg 301.
10. Applicable Legislation & Standards
•Work Health and Safety Act 2020 (WA)
•Work Health and Safety (General) Regulations 2022 (WA): reg 291 (high risk construction work), reg 299 (SWMS before the work), reg 300 (comply or stop), reg 301 (copy to the principal contractor), reg 302 (review), reg 303 (keep)
•Excavation: reg 304 (services information), reg 305 (excavation risks), reg 306 (support of trenches 1.5 m deep or deeper)
•Confined spaces: regs 62 to 77, including reg 66 (risk assessment) and reg 67 (entry permit)
•Falls, PPE and training: regs 78 and 79 (falls), regs 44 to 47 (PPE), regs 316 and 317 (general construction induction)
•Licensing: reg 81 (high risk work licences, where dogging applies to excavator lifts)
•The regulator for this work is WorkSafe WA.
•Pipework, trench support and test equipment follow the manufacturers' instructions and project drawings.
11. Worker Sign-Off & Acknowledgement
Each person below confirms they have read and understood this SWMS and agree to carry out the work in accordance with it.
Site supervisor - Priya Nair, Carraway Plumbing Pty Ltd
Signature: ________________________ Date: ____________________
Plumber 2
Signature: ________________________ Date: ____________________
Plant operator
Signature: ________________________ Date: ____________________