Underground Excavation Done Right

Avoid disrupting essential services with proper research and planning

This article looks at how to manage underground excavation work without interrupting essential services such as gas, water, sewerage, telecommunications and electricity. Here we discuss the Dial Before You Dig service, how to find buried utilities on site, and how to manage them during your project.

There’s also a list of reference links at the tail end of this article to help you locate specific information and regulations relating to your state.

Underground excavation risks

One of the most important elements of pre-demolition or construction planning is the location and disconnection of all essential services. Any excavation large or small has the potential to damage assets located around the work site, leading to power, phone, water or gas service interruptions, delays to the project and costly repairs. 

High pressure gas mains, live cables, toxic refrigerant lines and other hazards can pose a safety risk to workers on site and these hazards need to be mitigated as much as possible.

In certain situations such as with high voltage underground cables, there is also the sobering possibility of serious injury or death.

Using Dial Before You Dig to obtain information on the whereabouts of live cables and high pressure mains lines can significantly minimise these risks. The service is a great resource to find information about the work site that is not immediately apparent from above ground.

What is Dial Before You Dig?

Dial Before You Dig is a national service that aims to reduce damage to Australia’s extensive underground pipe and cable networks. The service is free and assists civil contractors, builders, excavation and demolition workers, landscapers and drainage specialists to locate buried services before any excavation or underground work takes place. This enables businesses and contractors to pinpoint and protect services in the area being excavated.

Dial Before You Dig helps coordinate information from asset owners and service providers (such as water authorities) on essential services that may be impacted by excavation or construction works in a specific area.

Underground essential services information can include the location and depth of pipes, cables or other associated plant. It can also include plans for any gas, water, sewerage, telecommunications, electricity, chemicals, fuel and refrigerant pipes or lines.

Excavation and the law

Most state WHS legislation, and indeed the national model WHS Regulations relating to excavation work, note that businesses or contractors must seek to find out more information before beginning excavation works.

These model national regulations state that “A person with management or control of the workplace must, before directing or allowing work to commence, take all reasonable steps to obtain current underground essential services information about the areas at the workplace where the excavation work is to be carried out. They must also obtain information about underground essential services in areas adjacent to the site of excavation and have regard for all of the information.”

This means that it is mandatory to locate pipes and cables before starting an excavation project. In short, you must:

• get information about the location and depth of underground cables, pipes and other essential services
• give the information to those carrying out the work
• make the information readily available for inspection, and
• keep the information until the work is complete, or for at least two years after a notifiable incident.

Not just for deep excavations

This policy applies to all types of excavation work, including bulk excavations more than 1.5 metres deep, trenches, shafts and tunnels. Additionally, it’s good practice to never assume that pipes and cables run underground in a straight line or at a set depth. Often existing structures or natural features may result in changes to the direction or depth of pipes or cables.

Finding out what’s under your site

Dial Before You Dig acts as an agent on behalf of a myriad of utilities and services organisations, who will ordinarily release cable, pipe and network drawings to you on request.

It’s easy to call the 1100 Dial Before You Dig hotline, or to submit an online enquiry. The simple online services asks you to provide some basic project details, mark out your area on the online map, and then view who owns the assets such as electricity providers or water authorities.

You can then contact the individual utility agency who will provide as much information as possible to help you locate and avoid essential services pipes and cables. Occasionally the agency’s own representatives may need to get involved and excavation approval given.

It’s worth noting that available information about existing underground essential services may not always be 100% accurate. Therefore it’s important that excavation methods include an initial in-person examination of the area to be excavated. With this purpose in mind, you may need to sample the area by exposing a short section of underground services. This is commonly done using water pressure and a vacuum system, known as potholing.

Best practice project management

Once you’ve got all the necessary plans and drawings, you can get to work on site. Underground essential services can be located using specialised underground locator tools such as electromagnetic cable locators and ground penetrating radar.

A pipe or cable locator such as the Leica Digicat 550i available from Jaybro can be invaluable in avoiding underground cables and pipes. Used in conjunction with the information from Dial Before You Dig, cable locators assist with estimating the depth of the underground infrastructure on your construction site.

Pipe or cable locators are of great help, but to establish the exact location of all underground infrastructure, you may need to pothole the area.  All electric, gas, water, sewer, steam and other service lines not required in the demolition process should be shut off, capped, or otherwise controlled, at or outside the building line, before demolition work is started.

Ensure you pothole precisely following the utility owner’s prescribed method. Then, protect the infrastructure by erecting barriers and marking the location of the exposed pipes, cables or wires. This will ensure the services are kept safe until the project is complete.

You should also ensure all workers are aware of the potholed area and that it is clearly fenced off, for example with temporary fencing or a pit guard.

Underground tapes, signage and labelling

If you’ve identified infrastructure clues such as grates, pits and marker posts on your site, check them closely for marker tapes that indicate buried water mains, electricity mains or sewer mains below ground. Signs noting any dangers such as ‘Danger – Underground Cables’ offer a clear indication.

You may need to use a lid lifter to access communications pits and isolate cables. Jaybro carries a range of lid lifters for communications pits and Telstra pits.

Within the pit, mains marker tapes indicate major services such as gas mains, or in shared trenches you might find communications, gas and electricity together, flagged with 3-way mains marker tapes. Network cables are generally surrounded by a conduit such as a fibreglass snake or communication rod. 

Ensure the open pit does not present a safety hazard by surrounding any open pits or drains with a pit guard.

Underground mains are ordinarily marked with detectable marker tapes. These warning tapes are sandwiched around a stainless steel tracer wire and are used to label communications, electricity, gas, water, sewer and stormwater mains. Mains marker tape is typically laid above underground services evenly between the service and the surface, providing a warning to machine operators before any damage to the service is caused.

Always refer to your local regulations and authorities for more information on how to control and safely manage services at your site once you have located the pipes and cables.

Once work is complete ensure all pit lids, manhole covers, grates and access covers are replaced and sealed if necessary with mastic or a similar sealant.

Keeping safety front of mind

The Dial Before You Dig program is an essential service for underground and civil contractors. Safety stickers that promote Dial Before You Dig act as a great reminder on site and help create a safer working environment.

Applied to heavy plant equipment, first aid kits and vehicles, they encourage workers to be mindful of underground services. Jaybro can supply a 5-pack of vinyl Dial Before You Dig stickers for you to stick on your equipment. Education and awareness are key and all staff should be familiar with regulations. 

Where can I find more information?

Australia wide: Safe Work Australia Model Code of Practice for Excavation Work

NSW: NSW: Workplace Health and Safety Regulation 2017, Section 304

“A person with management or control of the workplace must take all reasonable steps to obtain current underground essential services information about the areas where excavation work is being carried out and any adjacent areas, before directing or allowing the excavation work to commence.”