Locating Underground Services for Design and Site Investigation

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In New Zealand, with underground services being installed over quite a long time and changing standards and practices, services are all over the place. Unfortunately, this means service plans can be far from reliable and cannot always provide the accurate location of underground services such as water mains, power cables, gas lines, and communication services.

Underground service location and utilities detection reveals the location and depth of underground services in a safe, non-destructive manner to increase the safety of site investigations and efficiency of design.

Discovering the location of underground services and utilities

At Woods, we have a suite of leading-edge technologies available for our service locators to use when detecting and identifying underground services: 

  • Electromagnetic Induction (EMI)

EMI detects electromagnetic frequencies to identify the location of power lines and communication lines (a.k.a. “Passive locating”).

We can induce a current through conductive services (e.g. copper water pipes and communication lines) or on tracer cables attached to services and detect the resulting signal (a.k.a. “Active locating”)

Another form of active locating is using a Sonde. A sonde is a long cable which can be fed through services such as storm and waste water pipes and conduits. We then apply an EMI signal to the sonde which we can trace, revealing the location and depth of the target service.

  • Ground Penetrating Radar (GPR)

GPR technology uses radio frequencies to scan underground and detect anything out of the ordinary in the ground material which sticks out as a potential service.

We combine these technologies to logically work through the service plans and client data and locate or correct the location of underground services throughout the site.

Our team also complete a walk-through of the site beforehand looking for anything which could be a clue as to the location of where services meet up underground such as valve lids, fire hydrant lids, communication box lids.

The location of any utilities and services are marked using a safe, eco-friendly temporary spot marking paint (Soppec). We also have semi-permanent options for where markings are needed for longer than 2-8 weeks.

The benefits of underground service location and utilities detection

Health and Safety

The main benefit of underground service location is safety. Clearing the area of services before commencing geotechnical investigations or construction protects the health and safety of employees, contractors, and the community.

Avoid time delays, damage costs, and network interruptions

Once construction begins, striking a service which has been overlooked or is inaccurately reported on the service plan can cost hundreds of thousands of dollars to repair and add lengthy delays to your project. Underground service location enables you to mitigate this risk to keep your project within budget and on time.

Informed decision making and designs

This additional information also enables you to plan the design and construction around the services or incorporate them into the design. This helps you avoid discovering something later down the track which requires the designs to be changed.

Underground service location on the Eastern Busway project

One of the projects we are currently using this solution on is the Eastern Busway project - Auckland's second-biggest public transport project. Woods’ utility detection team is working with the geo-technicians on-site to locate and verify the location of critical services in the area. Locating these services will enable construction work to be completed safely further down the track and allow us to clear areas where the geotechnicians can safely drill a 20-30m hole or install a piezo for earth monitoring.

The future of underground service location

Industry regulation

At this stage, New Zealand does not have its own standard for locating and reporting of underground services. Woods and many other companies in the industry have adopted the Australian standard AS 5488 in reporting and practice, however, it only requires detection of services within a +/- 300mm horizontally and +/- 500m  vertically. The equipment Woods currently has available exceeds this standard of accuracy, but there is some room for improvement.

As the accuracy and reliability of underground locating equipment improves, the standard of accuracy required by locators in New Zealand will also have to improve, and this is something we are looking forward to being a part of in the future.

If and when a New Zealand standard is introduced, Woods is highly likely to be involved in having a say as to what goes into that standard as we are a prominent player in the survey industry. We are also working towards becoming certified locators at Woods to ensure we have a voice among other credited locators.

Emerging technology

Another thing we’re really looking forward to is combining underground locating with emerging technology such as augmented reality (AR). We expect that this will take off once service plans become a lot more reliable thanks to the new standard being brought in where the location of newly laid services have to be as-built to quite a high standard.

Having reliable data creates the opportunity for a locator to upload it to augmented reality software on their phone and be able to see on the screen where services run under the ground as they wander the site. This would be a great tool to help us verify what we think is there.

A reliable methodology for locating services

The nature of the science today is that it does not tell us exactly where a service is which means it does not yet replace the need for potholing or hydro vac investigations. However, as our knowledge, technology, and service plans improve it will become an incredibly reliable methodology for locating services.