Utility Surveying and Mapping
Utility Surveying (2D topography and 3D utility surveys)
When you’re planning any kind of design or excavation work on a major construction project, gathering detailed subsurface utility information (SUI) is essential. You’ll want to make sure that all site personnel are easily able to identify the locations of any underground utilities on your site. The best ways to do this is to have a comprehensive utility survey completed, complete with utility locate maps.
2d topographical utility maps provide clear, easy-to-read site maps of the underground services on site where 3D mapping is best viewed via computer or tablet as the all angles of the project can be observed by a simple command. With easy access to all the information they need, designers, excavators and construction managers can save time and money by eliminating the unnecessary risk of an accidental utility strike.
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Who should use utility mapping?
Why do I need to have utility mapping completed?
The consequences of a utility strike can be devastating – for the local community as well as your project. Striking gas pipes could lead to a serious explosion and fatalities; striking an electrical cable could cause serious injuries or fatalities to site crew and cause a major power outage in the area.
Regardless of how big the site or the planned work is, any excavation work at all could potentially damage assets located around the site. This damage could lead to project delays, service interruptions, and even fatalities.
It’s important to note that damage to an infrastructure asset isn’t limited to actually rupturing a pipe or cable. Damage can also include:
Any damage at all needs to be reported immediately, as if left unchecked it could cause a potential future incident. The best way to be certain that you aren’t going to damage the infrastructure assets is to have a comprehensive utility mapping service completed. That way, you can identify where any assets are located and proactively put in measures to prevent any damage.
What’s involved in a utility survey?
Locating underground utilities normally requires a combination of different methods so that you can successfully locate any underground pipes and cables on your excavation site. Geoscope use both electromagnetic and ground penetrating radar locating devices for 3D scanning in combination with the DBYD plans.
The exact techniques used will depend on the site itself but we find for most construction sites in the Sydney area, the combination of these methods, plus potholing is the most reliable combination to locate and map out the various conductive and non-conductive underground pipes and cables.
The end to end process normally includes:
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Utility StrategyYou need to have a strategy in place to protect any utilities and prevent damage. Ideally, you should be completing risk assessments and creating a strategy throughout the entire project from beginning to end:
It’s your responsibility to communicate this strategy and any outcomes of the risk assessment to your crew. If necessary, based on the risk assessment, you may need to make arrangements with each utility owner in order to disconnect, de-activate, isolate or discontinue the utility service before you begin any work close to the utility location.
Obtaining Dial Before You Dig (DBYD) plans
You can get hold of information about any underground utilities on your excavation site by submitting a ‘Dial Before You Dig’ request. It’s a free service, and very straightforward to use, but you’ll need to allow 48 hours to receive the plans from the asset owners, so make sure to work that into your project timescales.
You can submit your request with DBYD online, or by calling 1100 (toll free, during business hours). Make sure you have the details of the project ready. You’ll need:
Dial Before You Dig is a great starting point to give an indication of the location of any underground utilities on your site. But it is just that, an indication.
You can’t assume that the plans you receive are completely accurate, or that there aren’t any other underground pipes and cables on your site. They rarely show private lead in services to private properties and these are the pipes which need to be surveyed because of the lack of existing records.
Finally, not all asset owners are registered with the scheme, so relying on the plans alone can be a risky move.
On-site service detection
Once you have all the DBYD plans, you’ll need to carry out on-site utility detection. This can be done via various methods, but we highly recommend a combination of electromagnetic and ground penetrating radar locating methods.
Electromagnetic locating is the most common method used to detect conductive cables or pipes made from metallic materials – such as electrical wiring or copper pipes.
It’s most useful for utilities like electricity, water, and fuel lines. It works by passing a traceable current through the underground service by directly connecting or coupling a cable with a ring clamp.
This current is then carried by the conductor along the length of the pipe or cable. The receiver wand picks up the signal frequency and matches the output to verify the location.
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Ground penetrating radar (GPR) devices can detect underground services delivered via non-metallic pipes and cables. They work by pulsing electromagnetic waves into the subsurface that allows us to identify non-conductive underground pipes and cables. As many pipes and cables, including gas, are now made of materials like nylon and polyethylene, it’s essential to be able to locate these accurately.
Another reason we recommend using GPR in conjunction with electromagnetic detection methods is that even some metallic pipes and cables can be difficult to identify using electromagnetic devices in some circumstances. For example, areas with congested duct work and piping can distort the electromagnetic field and signals may reduce the location accuracy. Using GPR as well reduces this risk.
Both electromagnetic and GPR locating devices should only be used by certified locators like Geoscope technicians. Operating the equipment requires specialist training and knowledge, for accurate field interpretations.
There are occasionally underground utilities that are elusive even with these methods. That’s when it becomes imperative that you have your survey completed by experts with the right equipment, training, and experience.
Sometimes if a pipe or cable is inaccessible, conduction clips or clamps can’t be applied to it. In these circumstances you may need a general induction sweep. This is where an antenna is placed on the ground directly above the pipe or cable. The antenna then induces a signal into the pipe or cable that can be measured and tracked.
Then there are non-conductive pipes like fibre optics that don’t carry a signal at all. These can only be located by inserting a detectable duct rod into the line using an access point, such as a manhole.
Using all the appropriate methods in combination allows you to verify the accuracy of the DBYD plans, identify if there are any inaccuracies on the original DBYD plans, and also locate any additional underground utilities that were not identified on the plans.
It also provides the information we need to create a topographical 2D or 3D utility map that clearly marks the location of any underground utilities on your site.
Physical identification via potholing
Using locating devices is excellent for confirming the existence of pipes and, to some extent, the type of utility. However, in order to meet the highest safety standards you need to follow this up with visual verification. This is normally done via potholing: digging using non-destructive excavation methods in order to expose the utility.
Potholing is the safest, most effective non-destructive way of locating underground utilities. It serves several purposes:
We always advise that potholing is completed on site before you beging digging. Some asset owners do insist that you expose any pipes, cables or other assets before you begin work, so it’s imperative that you check any instructions provided with the DBYD plans.
Planning and consultation to protect utilities
Once you’ve identified and visually confirmed and documented the location of any underground utilities on your site, you’ll need to put together a strategy for ensuring that all work can be completed without disturbing them.
If the DBYD plans or were inaccurate (for example, an asset has been found to be located far from the recorded position on the plan), you should inform the asset owners so that they can amend their records.
You’ll also need to protect the exposed infrastructure. You can do this by erecting barriers, clearly marking the location, and clearly communicating the location to all site workers.
The location of any underground services should be marked on the ground of the dig site with the corresponding colour paint according to Australian Standard 5488:
- Yellow – Gas
- Orange – Power
- White – Communications
- Blue – Water
- Red – High Voltage
Depending on the type of utility, there are minimum safe approach distances that stipulate how close you can work to the existing pipe or cable. You may need to consult with the asset owners to gain advice or approval. In the case of gas pipes, the asset owners may even provide a representative on-site to ensure the safety and integrity of their infrastructure network.
Some other ways you may need to protect the underground services are:
If there is a minimum safe approach distance noted on the DBYD plans, you’ll need to follow the asset owner’s guidance on how to handle these ‘No Go Zones.’
To comply with your duty of care commitments, you must follow the No Go Zone restrictions for both underground and overhead services as set by the relevant State’s Safety Regulators or asset owners. If for any reason you can’t adhere to the minimum safe approach distance, you’ll need to contact the asset owner straight away so that they can provide additional guidance.
You can begin excavation only after you have followed the steps above and have adequate protective measures in place.
The different levels of utility survey according to the Australian Standard
It’s important to be aware of your duty of care obligations with regards to completing a utility survey. Your obligations under Health and Safety legislation are:
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.
The Australian Standard AS 5488 identifies 4 different classes of accuracy levels.
Utility must be located, then potholed. It must be physically sighted and measured.
Traced laterally, with depth detail, between two known points
from surface features
any other method such as sole reliance on DBYD plans
If you choose to rely solely on the DBYD plans you can only achieve Class D accuracy. Conducting a survey using electromagnetic methods and recording the depth and location achieves Class B. We highly recommend that you achieve Class A and complete a full investigation including potholing, so that you can fully satisfy all of your duty of care obligations.
Topographic 2D and 3D utility maps
We can provide you with both a 2D topography and a 3D model plan of the site utilities. Our utility maps are produced in AutoCAD and can be provided to you in PDF and dwg file formats.
The 2D plans are perfect to print and have the information ready in the field. Having the utilities mapped out onto the existing topography makes them clear and easy to read for all the site crew.
For when you need a more detailed picture of the depths and alignments of the underground utilities, the 3D plans provide all the information you need at a glance.
When you engage a locating company to provide both 2D and 3D utility maps for your excavation site, it helps you eliminate the risk of accidental utility strikes. Once the site is 3D scanned, and the AutoCAD designs completed, you’ll have all of the information you need for an effective utility strategy at your fingertips.
How long does it take to complete a utility survey?
When you’re managing a construction project with tight deadlines and budgets, it can seem like having a comprehensive utility survey done is expensive in terms of both time and money. However, the benefits and value of having a comprehensive survey far outweigh the minor inconveniences.
Imagine if you relied only on your DBYD plans, to then discover that there are pipes or cables under your excavation site, owned by a company that isn’t part of the DBYD scheme?
If you were lucky, it would cause delays and expense far larger than having a comprehensive survey completed. At worst? You could be responsible for thousands of homes and businesses losing power and or internet services and end up paying out huge sums in damages alongside serious delays.
When you think of it like that, a comprehensive survey is more than worth the reasonable amount of time and money it costs. Having all the subsurface utility information at hand before you break ground gives you peace of mind and ensures your duty of care is fulfilled.
Why choose Geoscope to complete the utility survey?
Geoscope specialise in the detecting the precise location of underground utilities, buried pipes and cables in Sydney and the surrounding areas. Using the latest technology and our vast experience we can locate all traceable underground services, pipes and cables, and various conductive and non-conductive utilities.