Regulations 304–306: WHS Excavation Work

Regulatory citation: Model Work Health and Safety Regulations, Chapter 6, Part 6.3, Division 3, Regulations 304–306 (Excavation work)

What Are the WHS Excavation Work Regulations?

Regulations 304 to 306 of the model WHS Regulations set specific duties for excavation work. Excavation work means work to make an excavation, or to fill or partly fill one. An excavation is a trench, tunnel or shaft, but not a mine, a bore covered by water laws, or a trench used as a place of interment.

A trench is defined as a horizontal or inclined way or opening that is longer than it is wide, is at least as long as it is deep, starts at and extends below the surface of the ground, and is open to the surface along its length. The three regulations cover underground essential services, general risk management and additional controls for trenches.

Why Excavation Rules Matter

Trench collapses can bury workers in seconds, and soil is extremely heavy. Striking underground gas, electricity or other services can cause explosions, electrocution or flooding. These regulations require services to be identified before digging and trench walls to be supported once depth reaches 1.5 metres.

Core Obligations

1. Obtain Underground Essential Services Information (r304)

Before directing or allowing excavation work to start, the person with management or control of the workplace must take all reasonable steps to obtain current information about underground essential services in the area of the excavation and adjacent areas. Essential services include gas, water, sewerage, telecommunications, electricity, chemicals, fuel and refrigerant in pipes or lines.

2. Share and Keep the Services Information (r304)

The information must be given to any person engaged to carry out the excavation work, such as the principal contractor and excavation subcontractors. It must be available to workers and for inspection, and kept until the excavation work is completed or, if there is a notifiable incident relating to the excavation, for 2 years after the incident.

3. Manage Excavation Risks Before Work Starts (r305)

A PCBU must manage risks associated with excavation work, including the risk of a person falling into the excavation, being trapped by its collapse, being struck by a falling thing, or being exposed to an airborne contaminant. The nature of the excavation, the nature of the work and the means of entry and exit must be considered.

4. Secure and Support Trenches at Least 1.5 Metres Deep (r306)

A PCBU who proposes to excavate a trench at least 1.5 metres deep must ensure, so far as is reasonably practicable, that the work area is secured from unauthorised access. It must also minimise the risk of the trench collapsing by ensuring all sides are adequately supported by one or more of shoring by shielding or another comparable means, benching, or battering. The model code of practice notes these controls may not be required where a geotechnical engineer advises in writing that all sides are safe from collapse.

5. Prepare a SWMS for Deeper Work and Tunnels

Construction work in or near a shaft or trench with an excavated depth greater than 1.5 metres, or a tunnel, is high risk construction work. A safe work method statement must be prepared before the work starts and followed during it.

6. Protect Adjoining Buildings and Structures

The model code of practice states work must not start until steps are taken to prevent the collapse of any building or structure that could be affected. Excavation below the footing level of a structure should be assessed by a competent person and supported by a ground support system they design.

Common Compliance Approaches

Before You Dig and Potholing

Request service plans through Before You Dig Australia, then confirm locations by hand digging or vacuum excavation, because plans may be inaccurate.

Trench Shields and Boxes

Use engineered shields or boxes sized for the trench depth, and keep spoil and plant back from the edge.

Safe Access and Edge Protection

Provide ladders or ramps for entry and exit, and barriers around open excavations to stop people and vehicles falling in.

Example: Excavation Work in Practice

A civil contractor is laying a new stormwater pipe 2.2 metres deep along a suburban street. The principal contractor obtains service plans and gives them to the excavation crew, who pothole to locate a gas main and a telecommunications cable. Because the trench will be deeper than 1.5 metres, the crew uses a trench shield and prepares a SWMS covering collapse, services strikes and traffic. Spoil is placed well back from the edge, and a ladder is kept inside the shield. The service plans stay on site until the work is finished.

Related regulations: WHS SWMS requirements, WHS principal contractor duties, OSHA excavations.

Note: This summary is based on the model WHS laws published by Safe Work Australia. The model laws only have legal effect once a jurisdiction adopts them. Most states and territories have adopted them with some variations, which can include different wording or regulation numbers, while Victoria has not adopted the model WHS laws and has its own OHS laws. Amendments to the model laws apply only once a jurisdiction adopts them. Always check the legislation and codes of practice that apply in your jurisdiction.

Frequently Asked Questions

At what depth must a trench be supported?

Regulation 306 applies to trenches at least 1.5 metres deep. All sides must be adequately supported by shoring, benching or battering. Shallower trenches still need their collapse risk managed under regulation 305.

Who must obtain underground services information?

The person with management or control of the workplace must take all reasonable steps to obtain it before directing or allowing excavation to start, then give it to those engaged to carry out the work.

How long must service information be kept?

Until the excavation work is completed or, if a notifiable incident relating to the excavation occurs, for 2 years after the incident.