What is Non-Destructive Digging when Locating Underground Utilities 


Excavation and construction projects require a lot of groundwork, and one of the essential aspects is locating underground utilities. 

Failing to identify buried utilities accurately can lead to significant disruptions, expensive repairs, and accidents, making the excavation process more time-consuming and costly. In Sydney, non-destructive digging (NDD) has become a popular technique used to investigate underground utilities without damaging them. 

This innovative technique provides accurate and efficient results, while minimising risks of damage, making it an indispensable process for excavation and construction projects.

What is Non-Destructive Digging (NDD)?

Non-Destructive Digging Services provided by Geoscope in Sydney, NSW

Non-destructive digging (NDD) is a process used to investigate and expose underground utilities without causing any damage. It involves the use of specialised equipment, which creates a slurry mixture of water and air that loosens the soil. This loosened soil is then removed from the excavation site through a vacuum system, allowing the operator to physically locate buried utilities accurately. 

NDD has proven to be an effective alternative to traditional digging methods, such as mechanical excavation or digging with bars and shovels, which has a greater potential to cause damage to the utilities and the surrounding area.

The Benefits of Using NDD Non-Destructive Digging include:

Traditional digging methods have the potential to lead to significant delays, while NDD can provide accurate results in less time. Moreover, NDD ensures the safety of the workers and surrounding communities, reducing the risk of accidents and injuries.

What are the uses of Non-Destructive Digging?

Non-Destructive Digging (NDD) is a versatile method used in several industries, including construction, mining, utilities, and infrastructure management. Some common uses of NDD include:

Locating underground utilities

NDD is commonly used to identify and locate underground utilities, such as:

Understanding where these underground services are exactly improves workers confidence in what’s below and helps to avoid damage to these utilities during construction or excavation activities.

Excavating in sensitive areas

NDD is ideal for excavation in sensitive areas such as heavy trafficable areas in urban and CBD areas as well as heritage sites, where traditional excavation methods may cause damage or disruption to the surrounding environment.


Removing debris and cleaning drains

NDD equipment and vacuum excavation trucks can be used to clean and remove debris from drain pits, culverts, and other underground structures without needing to physically enter the potential confined space.


Installing underground infrastructure

NDD is often used as part of the process to install underground infrastructure such as utilities that can be underbored using horizontal directional drilling. This is a less invasive method of installation than traditional trenching methods and can reduce the impact on the surrounding environment.

Overall, NDD is a safe, efficient, and environmentally friendly method of investigating and working with underground infrastructure. Its diverse range of applications makes it an essential tool for many construction and maintenance industries, enabling them to work with underground utilities and infrastructure with minimal disruption to the environment

Types of Non-Destructive Digging Methods

There are three primary types of non-destructive digging methods used in Sydney:

Hydro Excavation

Potholing Underground Utilities Service provided by Geoscope

This method involves using high-pressure water to loosen the soil and create a slurry mixture. The slurry is then removed through a vacuum system, leaving behind a clean excavation site.

Vacuum Excavation

Non-Destructive Digging Services provided by Geoscope in Sydney, NSW

This method involves using a vacuum system to remove soil and debris from the excavation site. This process is particularly effective for removing wet and dry materials.

Air Excavation

Hyrodexcavation process of locating underground services by Geoscope in Sydney

This method involves using compressed air to loosen the soil and create a vacuum. The soil is then removed through a vacuum system, allowing the operator to locate underground utilities accurately.

The Process of Non-Destructive Digging

NDD involves a specific process and equipment that allows for the safe and efficient excavation of the ground to locate underground utilities without causing damage.

Steps involved in NDD

Step 1. Electronically locating and identifying the location of the utility to be physically located.
Step 2. Creating a safe working location and the necessary safe work documentation.
Step 3. Preparing the NDD equipment, which includes a vacuum or hydro excavator truck and the necessary attachments such as hoses, lance, nozzles, and water tanks.
Step 4. Creating a slurry mixture using pressurised water to loosen and displace soil around the utility.
Step 5. Using the vacuum or hydro excavator to remove the slurry mixture and debris from the excavation area.
Step 6. Inspecting and verifying the location, depth, and condition of the utility.
Step 7. Documenting and recording the findings.
Step 8. Backfilling the utility.
Step 9. Reinstating the surface.
Step 10. Making the site safe.


Equipment used for NDD includes hydro or vacuum excavator trucks, which are specially designed vehicles equipped with high-pressure water jets, air compressors, and vacuum systems. 

These trucks also have long hoses with nozzles to direct the water and air into the ground to create the slurry mixture and excavate the soil around the utility.

The workers must wear personal protective equipment such as gloves, hard hats, and safety glasses to protect them from flying debris. 

The excavation site must be properly barricaded, and warning signs should be posted to alert the public of the work being done.

What type of Utility Investigations can Non-Destructive Digging (NDD) do?

Non-destructive digging (NDD) can be used to conduct two types of utility investigations: Potholes and Slit trenching, are the most common investigations used to locate and verify underground utilities and varying combinations of the both.

What is a Utility Investigation Slit Trench?

Slit Trenching Utility Investigation Method of locating underground utilities service provided by Geoscope in Sydney, NSW

A utility investigation slit trench is a type of excavation that involves digging a narrow trench, typically around a metre deep, or however deep the utility is, and however long the particular area is, that is required to expose the utilities along the path being investigated.


Once the trench is dug, utility surveyors can inspect the exposed utilities to determine their utility attributes such as the location, size, depth, condition, asset owner, and other important data that needs to be recorded for the utility survey.

The slit trenching method is often used when other electronic locating methods, such as ground-penetrating radar or electromagnetic detection, are not sufficient, or when a more detailed Quality Level-A (QL-A) utility information is needed for accuracy during the project’s design phase.

What is a Utility Investigation Pothole?


A utility investigation pothole is a small excavation made in the ground to expose and investigate underground utilities such as pipes, cables, or other buried infrastructure. 


Using NDD, a pothole involves digging a relatively small hole, usually less than 200 mm in diameter, to expose the utilities. 

Like the slit trenching method, the potholing method is commonly used when there is a need to confirm the location and depth of underground utilities or to identify any potential problems or defects. 

Potholing is most effective when the location has been previously marked and located by EM and GPR locating methods or when a Quality Level B subsurface utility information survey has been completed, and it is time to move on to the verification stage.

Why use Non-Destructive Digging over Mechanical Excavation around utilities?

NDD has several advantages over traditional mechanical excavation methods, including safety and efficiency. 


NDD reduces the risk of accidents and injuries that can occur during mechanical excavation, which can involve heavy equipment being used near fragile underground utilities that may be difficult to detect or locate. 


With NDD excavation, locations can be targeted exactly where you want to find the information on buried utilities below or when working in specific areas trying to avoid certain utilities.

NDD is a reliable and efficient alternative to traditional excavation methods, and it undoubtedly surpasses them in terms of safety and effectiveness. 

TRaidtional Method od locating underground utilities using hand and shovel

In comparison, hand digging with a shovel or other mechanical excavation methods can be time-consuming and potentially hazardous, risking potential damages to buried utilities

Therefore, NDD remains the preferred option for safe and efficient excavation of underground infrastructure.

The Importance of Non-Destructive Digging – NDD in Sydney

Sydney’s utility infrastructure is extensive, with a vast network of water, gas, electricity, and telecommunication lines running underground. Damage to any of these utilities can cause significant disruption and safety hazards.

NDD is crucial in Sydney to prevent damage to these utilities and ensure the safety of the workers and the public. By using NDD, construction and excavation crews can locate underground utilities accurately and avoid accidents and injuries.

Regulations and Compliance

Non-Destructive Digging, although a lot safer than traditional mechanical excavation, does have very minor risks which have been outlined by critical underground infrastructure such as high-pressure pipelines in APA and Jemena as well as certain telecommunication networks that have the potential for working near direct buried fibre optic cables that could be found in Telstra and Optus documentation.

This safe working procedure and Non-Destructive Digging documentation outline the safe working pressures and the proximity of the nozzles to the underground utility, which ensure that the excavation work is done safely and efficiently. 

Safe Work and regulatory compliance requirements must be adhered to as with any work being completed within the construction industry in Sydney, and penalties for non-compliance can be severe.

The Australian Standard AS 5488 provides a framework for subsurface utility information management and specifies four quality levels of information that can be obtained through utility locating techniques. 

The Quality Level-A location level provides the most accurate information on the utility’s location, size, depth, and condition, and using NDD to locate underground utilities to QL-A goes hand in hand.


Along with following Safe Work and Critical infrastructure asset owner’s procedure outlines, operators using NDD must also comply with local and government regulations and obtain necessary permits before performing any excavation work. Road and footpath opening permits are required to cut and excavate out in the road reserve that is maintained by local municipalities. 

If you want to learn more about Australian Standard AS5488, this article is for you!

The Australian Standard AS5488

In this article, we will be talking about Australian Locating Services and the Australian Standard (AS5488).

Non-destructive digging is a safe and efficient method of locating and verifying underground utilities. It involves a specific process and equipment that allows for excavation without causing damage to the surrounding utilities. NDD has several advantages over traditional mechanical excavation methods, including accuracy, efficiency, and safety.

In cities like Sydney, where utility infrastructure is extensive, NDD plays a crucial role in preventing damage to underground utilities and ensuring the safety of workers and the public. It is essential to comply with Australian Standards and local regulations to ensure that the excavation work is carried out safely and efficiently.

In summary, prioritising NDD in construction and excavation work is vital for the success of the project and the safety of all involved. If you have any inquiries or feedback, please do not hesitate to comment below or email us at info@geoscopelocating.com.au. For the most reliable and trusted NDD service provider in Sydney, we highly recommend Geoscope. Click the link below for more information, or fill in the form provided to contact them directly.

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Patricia Cupiado

Co-Author of this Article

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