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Underground: understood

Making sense of a complex web.

Frequently Asked Questions

What is utility location?

Utility location is a general term used to describe the process of finding and marking underground services and objects.

Buried services include the most obvious utilities such as telephone, power, water, gas, sewer systems and stormwater as well as a few less obvious services such as fuel lines, cable TV, and storage tanks. The location method depends mostly on the type of service that needs to be found as well as the environment where the service is buried.

The way in which the location of a service is shown depends on the needs of the client. In its most simple form, the location is simply marked on the ground with temporary marking paint. If the clients needs something more specific, the location of services can be surveyed and provided in the form of a plan or drawing.

Can all services be located?

How easily a service can be located is dependent on a variety of factors. Some of the things that determine whether a service can be located are:

  • the type of service and what it is made of - Services that have a metal component such as power cables, older copper phone lines, iron manhole covers, cast iron gas or water mains can often be more easily located. Non metallic services such as plastic or PVC pipes, old clay or asbestos cement pipes, and fibre optics can limit the methods of location,
  • what other services are close by - When services are located together or there is a large number of services in close proximity then it can sometimes be difficult to differentiate between individual services without actual digging, and
  • how deep the service is - Common services, such as power, gas, and telephone are often buried at a generally agreed depth, although this can never be relied on when locating. Some services, such as sewers and stormwater will be buried at a much greater depth and are much hard to locate. Deeper services often require special techniques to locate and identify.

What is Ground Penetrating Radar?

Ground penetrating radar (GPR) is a technology that uses radio waves to identify objects underground. Different frequency radio waves can be directed into the ground so that objects underground reflect back signals to the receiver at ground level. Objects underground such as cables or pipes have a certain appearance that a trained operator will recognise. GPR can help locate and identify underground services that can't be found by other means such as electromagnetic (EM) detection.

GPR is influenced by many factors and is not appropriate for every situation. Certains soil types, high water tables, and service types can all affect how successful GPR will be.

What does NULCA Accredited Locator mean?

NULCA or National Utility Locating Contractors Association is an Australian professional body for companies and individuals that provide underground service and asset location. NULCA aims to ensure that all of its members meet a high level of competency and professionalism. One way that they try to achieve this is to provide a test of competency for its members. This accreditation is recognised in Australia under the Australian Qualifications Framework (the equivalent of New Zealands NZQA). ULS is currently an accredited member of NULCA Australia.

What is AS5488?

AS5488 or Australian Standards AS 5488 - 2013 Classification of Subsurface Utility Information is a standard that establishes a framework for describing the information relating to underground services and the different levels of quality that are possible with the different methods that a service might be located and marked.

The standard defines levels of quality that range from a low or less accurate service location (Quality Level D) through to the best or most accurate level (Quality Level A).

In general, ULS works to a Quality Level B which involves an active method of locations such as electromagnetic (EM) detection and Ground Penetrating Radar. Each Quality Level has a degree of accuracy that defines the margin of error that can be expected horizontally and vertically.

How will services be shown on the ground?

Generally, services will be marked on the ground to show where they have been located, using temporary marker paint.

Certain colours have been assigned to be used to indicate different types of services. The Department of Labour published the acceptable colours and symbols in the Guide for Safety with Underground Services. ULS has created a handy A5 reference page that shows the current colours and designations that should be used by convention within New Zealand.

Got more questions about underground service location or how ULS might be able to help you: