Landscape Drainage Trench Install SWMS

Installing landscape drainage systems — including agricultural pipe, French drains and surface stormwater pits — involves excavation, manual handling of aggregate and pipe, and working in trenches that frequently become wet and unstable. Even at depths under 1.5 metres, ground collapse, struck-by hazards from excavator buckets, and musculoskeletal injury from repetitive shovelling and lifting are well-documented causes of serious harm and fatality in the Australian landscaping sector. Under WHS Regulation 2025, any excavation work — regardless of depth — that forms part of construction work is classified as High Risk Construction Work under section 291, triggering the mandatory requirement for a Safe Work Method Statement before work commences. The SWMS must be prepared in consultation with workers, identify the specific hazards of the trench install, document the controls applied under the hierarchy of control, and remain available at the workplace for the duration of the activity. This document provides a compliant, trade-specific SWMS framework that landscaping PCBUs and crews can apply, customise and sign on to for residential, civil and commercial drainage installs.

Hazards identified

7 hazards covered, sorted by priority.

Control measures

Hierarchy-of-controls order: elimination → substitution → isolation → engineering → administrative → PPE.

1. 1Elimination — Where feasible, design drainage runs to avoid existing service corridors and use vacuum excavation rather than open trenching near identified asset locations.
2. 2Elimination — Eliminate worker entry into trenches over 1.2 m by laying pipe and aggregate from surface using long-handled tools and excavator-assisted placement.
3. 3Substitution — Substitute heavy 20 kg aggregate bags with bulk-bag delivery and excavator bucket transfer to remove repetitive manual carry from the task.
4. 4Engineering — Batter, bench or shore trench walls to AS 5047 and the SafeWork excavation Code of Practice when entry below 1.0 m is unavoidable in unstable ground.
5. 5Engineering — Install rigid trench edge protection, spoil setback of minimum 600 mm, and ladder access every 9 m of trench length per excavation Code.
6. 6Administrative — Obtain and verify Dial Before You Dig service plans within 28 days of works; conduct potholing of all marked services before mechanical excavation commences.
7. 7Administrative — Conduct documented pre-start briefings using this SWMS, with sign-on by every worker and a daily trench inspection logged by the competent person.
8. 8Administrative — Enforce 3 m exclusion zone around operating excavator with dedicated spotter using two-way radio for any worker approach into the swing radius.
9. 9PPE — Provide and enforce hi-vis Class D/N garments, steel-cap waterproof boots, cut-resistant gloves, safety glasses and P2 respirators during dry cutting operations.
10. 10PPE — Supply hearing protection rated SLC80 ≥ 22 dB for sustained plant operation and hard hats compliant with AS/NZS 1801 for all in-trench personnel.

Applicable Codes of Practice

High-Risk Construction Work triggered

Worked example

On a Tuesday morning at a suburban residential renovation, a two-person landscaping crew is installing 32 metres of agi-pipe French drain along a sloping rear boundary, terminating at a new 600 mm stormwater pit at the side fence. Before any plant starts, the leading hand pulls out this SWMS at the tailgate and walks the apprentice through each of the seven listed hazards, marking the trench collapse and underground services items as the day's critical controls because the Dial Before You Dig plans show a 240 V consumer mains running parallel to the planned trench line. They confirm the mini-excavator operator has potholed the cable by hand at three locations, the spoil is being placed 700 mm back from the trench edge, and a ladder is positioned at the pit end. Both workers sign on to the SWMS and the document is clipped to the site board. Mid-morning, persistent rain begins and the trench walls in the sandy fill start sloughing. The leading hand stops work, refers back to the engineering controls section of the SWMS, and the team installs an aluminium trench shield in the deeper pit section before any further entry. The SWMS is annotated with the change, re-signed, and work resumes safely — demonstrating the document functioning as a live field control, not a filing-cabinet exercise.

Related legislation

• WHS Act 2011 (model)
• WHS Regulation 2025
• AS 4373 — Pruning of amenity trees; Managing Risks of Hazardous Chemicals CoP

Frequently asked questions