Culvert & Pit Installation SWMS

Culvert and pit installation is the trenching, laying, jointing and connection of stormwater and drainage pipes, culverts and junction pits. It is high risk construction work under the WHS Regulation because it is carried out in trenches deeper than 1.5 m, may require confined-space entry into deep pits, is performed on or near pressurised gas, chemical/fuel and energised electrical services, and involves the movement of powered mobile plant (s291), so a SWMS is mandatory (s299). The dominant hazard is trench collapse: a wall failure onto workers laying or jointing pipe, or during bedding and haunch compaction, is the characteristic fatality, and a person in an unsupported trench over 1.5 m cannot self-rescue. Around it sit unit-placement crush (a pipe or pit unit crushing the crew during lowering), service strikes on gas, electrical, water, sewer or telecom, confined-space atmospheres in deep junction pits (oxygen deficiency, H2S from connected live drainage), and manual-handling and access strain in the confined trench. The SWMS controls the trench support, service location, confined-space entry, lifting and manual handling. It supports the engineered design to AS 3725 and AS/NZS 3500 and does not replace it. It is supplied in eight jurisdiction editions, each citing its own Act, Regulation and regulator.

Hazards identified

8 hazards covered, sorted by priority.

Control measures

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

1. 1Elimination — Use trenchless (bore/thrust) methods or pre-assembled pit systems where the ground allows so open-trench entry is minimised
2. 2Substitution — Substitute a trench shield or hydraulic shore for hand work in an open unsupported trench, and mechanical lowering for manual pipe handling
3. 3Engineering — Shoring boxes or hydraulic shores, or battering per soil type and depth, with spoil set back at least the trench depth (minimum 600 mm behind a supported edge)
4. 4Engineering — Certified lifting gear and taglines for lowering pipes and pit units, with no hands beneath the load
5. 5Engineering — Positive services location before excavation, and forced ventilation and atmospheric monitoring for any deep-pit entry
6. 6Administrative — Soil classified by a competent person before excavation, a permit to enter, and no entry to an unshored/unbattered trench over 1.5 m
7. 7Administrative — Confined space entry permit, standby attendant and rescue plan for deep-pit entry
8. 8Administrative — Manual-handling controls and safe access/egress (ladders) within the supported zone
9. 9PPE — Type 1 hard hat and Type R day/night high-visibility for all trench work
10. 10PPE — Air-supplied or appropriate RPE and a retrieval harness for confined-space pit entry

Applicable Codes of Practice

High-Risk Construction Work triggered

Worked example

At 7:00 am a drainage crew from Watershed Civil begins laying a stormwater line into a junction pit. The trench will run 2.1 m, so it is shored with a box set in before anyone enters, and spoil is placed a full trench-depth back from the edge. Dial-before-you-dig plans are checked and a sewer main crossing the line is potholed and protected. Each pipe is lowered on certified slings with taglines, and the crew keep hands clear as it is guided onto the bedding — no one is beneath the load. The deep junction pit is treated as a confined space: it is isolated from the live drainage where possible, the atmosphere is tested for oxygen and H2S, forced ventilation runs, and entry is under permit with an attendant and retrieval system. A ladder gives egress within the shored zone, and the excavator is kept separated from the crew by a spotter. Jointing in the trench is broken into manageable lifts to control manual-handling strain. The line and pit are connected and signed off, and the trench is barricaded at shift end.

Related legislation

• WHS Act 2011 (model)
• WHS Regulation 2025
• Excavation Work Code of Practice
• AS 3725 Design for installation of buried concrete pipes and structures

Frequently asked questions