Quick answer: Working near underground services requires careful planning and typically several SWMS, particularly where excavation is involved. Striking a buried gas main, energised electrical cable, pressurised water main, or communications duct can cause explosion, electrocution, flooding, service outages, and serious injury or death. The SWMS documents you need will depend on the excavation method, depth, proximity to known services, and the plant and equipment involved.
Last reviewed: June 2026 by the BlueSafe Technical Team. Reflects current Australian WHS requirements.
Underground services represent one of the most serious hazards on civil and construction sites. Gas, electrical, water, and communications infrastructure is present beneath almost every urban and suburban work site, and the consequences of striking the wrong line can be catastrophic — for workers, bystanders, and property. Good safe work method statements for underground services work are not a box-ticking exercise. They are working documents that explain exactly how the team will locate services, verify their position, approach them safely, and respond if something unexpected is encountered.
At a glance
| Item | Summary |
|---|---|
| SWMS required? | Commonly yes — excavation at 1.5 m or more is HRCW; services hazards may require SWMS at shallower depths |
| Licence required? | Depends on task — high risk work licences required for certain plant operations; specific requirements apply to working on or near energised electrical infrastructure |
| HRCW triggers | Excavation to 1.5 m or more; work near energised electrical installations or services; mobile plant use |
| Typical tasks | Services location, cable locating, potholing, hand digging, hydro excavation, bulk trenching, under-road boring |
| Main SWMS focus | Services identification and marking, controlled excavation methods, exclusion zones, emergency response |
| Main risk | Striking gas mains (explosion, fire), energised electrical cables (electrocution, arc flash), water mains (flooding, excavation collapse), communications conduits (service damage, liability) |
Recommended SWMS set
The table below lists SWMS that are commonly needed for work near underground services. The exact combination will depend on the scope of work, excavation method, known service types, and site conditions.
| SWMS | Why it may be needed |
|---|---|
| Location of Underground Services SWMS | The foundational document for any work involving buried infrastructure — covers the DBYD/Before You Dig search process, cable locating equipment, service marking, and ground truth verification before excavation begins |
| Excavation Near Underground Services (Potholing) SWMS | Covers the controlled hand digging or vacuum excavation used to physically expose and confirm service locations before bulk excavation — one of the most critical steps in underground services risk management |
| Excavation and Trenching SWMS | Required where bulk excavation or trenching is being carried out — covers trench depth, battering or shoring, spoil placement, and the additional controls needed when known services are in the vicinity |
| Hydro Excavation SWMS | Where a hydro excavation unit (vacuum excavator) is used to safely expose underground services using pressurised water and a vacuum system — the preferred method for non-destructive digging near services |
| Under-Road Boring SWMS | Where horizontal directional drilling or manual boring is used to install conduits or services beneath a road or other surface without open-cut excavation — involves proximity to existing buried infrastructure across the bore path |
| Mobile Plant SWMS | Where excavators, backhoes, loaders, or other mobile plant are being operated near or above known underground services — plant operators must understand service locations and the exclusion zones that apply |
When does working near underground services need a SWMS?
Under Australian WHS legislation, a SWMS is required for High Risk Construction Work (HRCW) on a construction project. Work near underground services commonly triggers HRCW in several ways.
Excavation to 1.5 metres or more
The model WHS Regulations list excavation to a depth of 1.5 metres or more as a specific HRCW category. Any trench, pit, or excavation that reaches or is intended to reach this depth requires a SWMS before work commences. Where underground services are known or suspected to be present, this requirement is supplemented by the need to address the additional hazards those services introduce.
Proximity to energised electrical infrastructure
Work near energised electrical installations or services is independently listed as HRCW under the model WHS Regulations. This includes work near buried electrical cables — not only overhead lines. Where excavation is being carried out in proximity to buried electrical infrastructure, the HRCW trigger for energised services applies regardless of the excavation depth.
Mobile plant operations
Excavators, backhoes, vacuum excavation units, and directional drilling rigs are all mobile plant. Their use on a construction project commonly triggers the mobile plant HRCW category. When mobile plant is operating above or near underground services, the potential for a single uncontrolled movement to strike a gas main or electrical cable requires specific controls that should be addressed in the SWMS.
Shallower excavations near high-consequence services
Even where excavation depth does not reach 1.5 metres, work near high-consequence infrastructure — such as high-pressure gas transmission mains, high-voltage electrical cables, or fuel pipelines — warrants documented safe work methods given the potential severity of a strike. Duty holders should consider whether a SWMS is appropriate for any excavation work where the consequences of striking a service could be catastrophic.
Note on jurisdiction
Requirements vary across states and territories. Victoria operates under separate WHS legislation to the model WHS framework used in NSW, Queensland, South Australia, Western Australia, Tasmania, the ACT, and the Northern Territory. Network asset owners and gas and electricity distributors may also impose specific requirements for work near their infrastructure, independent of WHS legislation. Duty holders should confirm applicable requirements with the relevant WHS regulator and any affected asset owners before commencing work.
Common hazards when working near underground services
The hazard profile for underground services work is dominated by a small number of high-consequence events that can occur with very little warning.
- Striking a gas main — contact with a buried gas pipe can cause an immediate gas release, with risk of explosion or fire from ignition by plant, a spark, or a nearby source; unignited gas in an excavation creates an asphyxiation and delayed ignition risk
- Striking an energised electrical cable — contact with a buried electrical cable can cause electrocution of the operator or nearby workers, arc flash, plant damage, and fire; the cable may remain energised and dangerous after contact
- Striking a pressurised water main — rupturing a water main can rapidly flood an excavation, destabilise trench walls, and create a collapse risk for any workers in the excavation
- Striking a communications duct or conduit — damage to telecommunications, fibre, or data infrastructure can cause significant service outages and substantial liability; conduits may also carry energised low-voltage conductors
- Inaccurate or incomplete services information — DBYD/Before You Dig plans show registered infrastructure but not all buried services are accurately recorded; unregistered or abandoned services are a persistent hazard
- Service depth variation — ground movement, past road works, and installation tolerances mean services are often found at depths different from those shown on plans
- Excavation wall collapse — once a trench or pit is opened, there is a risk of wall collapse or ground movement, particularly in unstable soils or near vibrating plant; workers in an excavation are at risk of burial
- Mobile plant strike — excavator buckets, auger flights, and boring heads can strike services with significant force before the operator is aware
- Confined space hazards — gas accumulation in an excavation, pit, or boring entry point can create a confined space atmosphere requiring monitoring and entry controls
- Manual handling and musculoskeletal injury — hand digging near services is physically demanding and often performed in awkward positions in confined excavations
Controls for working near underground services
The hierarchy of controls for underground services work is well established in Australian practice. Key controls include:
Before breaking ground:
- Complete a Before You Dig Australia (formerly Dial Before You Dig) search and obtain plans for all registered services in the work area
- Conduct an additional site-specific services search and cross-reference DBYD plans against any available council, asset owner, or project drawings
- Mark out all known service locations on the ground surface in accordance with the relevant colour code before any excavation commences
- Use a cable locator (electromagnetic locating device) to verify service positions, particularly where plans indicate services are near the proposed excavation
During excavation:
- Pothole (expose by hand digging or hydro excavation) to physically confirm service location and depth before using mechanical plant within the exclusion zone around known services
- Observe the required minimum approach distances for mechanical excavation near different service types — the relevant asset owner, network operator, or applicable code of practice will specify these distances
- Use hand digging only within the exclusion zone around a confirmed service location
- Where hydro excavation (vacuum excavation) is available, use it as the preferred method for exposing services — it is non-destructive and substantially reduces strike risk compared to mechanical digging or hand digging with metal tools
- Ensure plant operators are briefed on service locations, service marking, and the controls that apply when working near services
- Do not allow workers to enter an excavation near a gas line until the atmosphere has been checked and confirmed safe
Permits and authorisations:
- Obtain an excavation permit or approval from the relevant asset owner or network operator where required — many electricity distributors and gas network operators require notification or approval before excavation within specified distances from their assets
- Confirm whether a permit to work or network asset protection agreement is required for the specific work location
Other documents you may need
A SWMS alone is not sufficient for underground services work. The following supporting documents are commonly required or expected.
| Document | When typically needed |
|---|---|
| Before You Dig / DBYD search results and plans | Before any excavation — provides information on registered service locations; legally required in most jurisdictions |
| Site-specific services search results | Where additional sources beyond DBYD are available — council records, asset owner drawings, as-constructed plans |
| Excavation permit or asset protection agreement | Where required by the network operator or asset owner for work near their infrastructure |
| Site risk assessment | Before excavation commences — identifies the specific services present, their locations and depths, and the controls to be applied |
| Plant pre-start checklists | For all mobile plant on site — excavators, hydro excavation units, boring rigs, and any associated plant |
| Confined space risk assessment and entry permit | Where gas accumulation or atmosphere hazards are identified in excavations, pits, or boring entry points |
| Emergency response plan | Site-specific plan covering how to respond to a gas strike, electrical contact, flooding, or trench collapse — including emergency contacts for the relevant service providers |
| Toolbox talk record | Pre-start safety discussion with the crew covering service locations, exclusion zones, and emergency procedures for that day |
Example scenario
A civil contractor is engaged to install a new telecommunications conduit along a suburban street. The route requires a trench approximately 600 millimetres deep and 60 metres long. DBYD plans indicate a water main, a gas main, and low-voltage electrical cables are within the work corridor. An excavator will be used for bulk trenching, with hand digging required when approaching services.
For this job, the crew should consider having in place:
- A Location of Underground Services SWMS covering the Before You Dig search, cable locating, and surface marking of all known services before the excavator is started
- An Excavation Near Underground Services (Potholing) SWMS covering the hand digging or hydro excavation approach to expose and confirm the depth and exact location of the water main, gas main, and electrical cables before mechanical excavation proceeds in those areas
- An Excavation and Trenching SWMS covering the bulk mechanical trenching, trench wall stability, spoil placement away from the trench edge, and the controls that apply when the excavator is working within the corridor containing known services
- A Mobile Plant SWMS covering the excavator operation, operator briefing on service locations, and the requirement to stop and hand dig when approaching the marked exclusion zones
- A Before You Dig search results package retained on site for reference
- A site risk assessment identifying each known service, its mapped location, the potholing confirmation results, and the exclusion zones applied to each service type
- An excavation permit or asset protection approval from the gas distributor and electricity network operator where required
- A pre-start toolbox talk record each day covering service locations, controls, and emergency contacts for the gas distributor and electricity distributor
This combination gives each major activity its own clear document, ensures services are systematically identified before work begins, and documents the controls that keep workers away from the most dangerous services in the corridor.
Frequently asked questions
Do I need a SWMS before digging near underground services?
In most cases yes. Excavation at or beyond 1.5 metres is listed as High Risk Construction Work under the model WHS Regulations, and working near energised electrical services is a separate HRCW trigger. Even at shallower depths, the potential consequences of striking a gas main or live electrical cable mean that documented safe work methods are widely expected by WHS regulators and asset owners. A SWMS for underground services work should address how services have been identified, how they will be located on the ground, the exclusion zone controls for mechanical and hand digging, and the emergency response procedures if a service is unexpectedly encountered.
Is excavation High Risk Construction Work?
Excavation to a depth of 1.5 metres or more is specifically listed as HRCW under the model WHS Regulations, which means a SWMS is required on a construction project before that work starts. Excavation at shallower depths may also trigger HRCW if it involves work near energised electrical services or use of mobile plant. Where a trench or pit is being dug near underground services, the combination of the excavation hazard and the services hazard means that documented controls are important regardless of the depth trigger.
What is Dial Before You Dig and is it mandatory?
Before You Dig Australia (which incorporates the former Dial Before You Dig service) is a national referral service that connects those planning to excavate with the registered owners of underground infrastructure in the area. Completing a search provides plans showing the approximate locations of buried services. In most Australian jurisdictions, contacting the service before excavation is a legal requirement, not just a best practice. Importantly, the plans provided show registered infrastructure only and should always be treated as approximate — on-site cable locating and physical verification by potholing are necessary steps before relying on plan information for mechanical excavation decisions.
Can one SWMS cover all underground services work?
Not usually. The location phase (DBYD search, cable locating, surface marking), the potholing phase (hand digging or hydro excavation to physically expose services), bulk mechanical excavation, hydro excavation, and under-road boring each involve distinct methods, hazards, and controls. Compressing all of these into a single document tends to produce a SWMS that is too broad to be practically consulted during any one task. A set of purpose-built SWMS — one for each major method — paired with a site risk assessment that ties the service-specific information together at the job level is typically the more effective approach.
Need help choosing the right SWMS?
The SWMS set you need for underground services work will depend on the excavation method, the types of services known or suspected to be present, the plant and equipment on site, and the specific site conditions. Browse the individual SWMS products below or use the links to find out more.
Underground services and excavation SWMS:
- Location of Underground Services SWMS
- Excavation Near Underground Services (Potholing) SWMS
- Excavation and Trenching SWMS
- Hydro Excavation SWMS
- Under-Road Boring SWMS
Plant and equipment SWMS:
Not sure which combination is right for your job? Use the SWMS selector to find products based on your trade and tasks, or work through the WHS self-check to identify gaps in your current documentation.
This guide provides general information only and does not replace project-specific risk assessment, legal advice or consultation with the relevant WHS regulator. Duty holders should assess the actual work, site conditions, workers, plant, substances and applicable state or territory requirements before selecting or using a SWMS.