Utility locating is the process of identifying through investigating reference plans, visual indicator assessment and geophysical equipment techniques sub surface presences including underground utilities. These mains may include lines for telecommunication, electricity distribution, natural gas, cable television, fibre optics, traffic lights, street lights, storm drains, water mains, and wastewater pipes.
Multiple factors may affect the possibility of locating unplanned or unknown utilities.
- It may not be recorded in any reference plans making it difficult to know what you are looking for and the applicable geophysical technique cannot be applied.
- The unknown is comprised of non-conductive material e.g. PVC/PE/Concrete which cannot be picked up by and electromagnetic locating device.
- It is an abandoned conductive material which is not being energised, e.g. a cut power cable, or cut abandoned main which is not earthed.
- It is an abandoned conductive material and too small to reflect radio signal, e.g. abandoned two-pair cable.
- Poor or unsuitable ground conditions for ground penetrating radar (GPR) scan to identify. It is hard for GPR to work effectively under poor ground conditions which include clay, iron, salt, water, etc. Especially if the unknown is not recorded on a plan.
- There may not be adequate time or budget to grid scan an area and reproduce detailed sub surface modelling.
In the process of locating or performing a ground penetrating radar (GPR) scan, the technicians keep their head down, concentrating fully on the investigation and equipment feedback task. For this reason, it’s not possible for them to also stay alert and aware of any oncoming traffic.
It often happens that there are utilities running across the width or length of a road that require scanning. As such it is very dangerous for locators to conduct scanning in or along a roadway without a spotter or traffic management in place.
In terms of exposing utilities to verify the precise location during a potholing task, there are often exposed holes and live-running machinery and assorted equipment on the ground.
With no traffic management to zone off the area from pedestrians, accidents can happen.
Having traffic management in place to ensure the safety of persons near the work area is a legal responsibility of contractors under the Occupational Safety and Health Act 1984 (OSH Act).
Dial Before You Dig is a FREE national referral service to assist anyone who intends to work around any infrastructure asset(s) to prevent damage and disruption to Australia’s vast infrastructure networks which provide essential services we use every day.
It’s a single point of contact to access information about any infrastructure networks at the planned project site from registered Dial Before You Dig members without a need to contact them individually.
You can log a Dial Before You Dig enquiry by calling 1100 or by visiting www.1100.com.au.
Yes, court proceedings may commence against individuals and/or companies for the recovery of the cost of repairing or reinstating damaged assets where carelessness appears to be a contributing factor including not using an approved or accredited locator.
It’s imperative that you have an expert, accredited GPR technician complete your GPR utility survey to minimise the risk of strikes.
A GPR technician will accurately estimate the location, depth and nature of subsurface pipes, cables and utility structures.
They will also facilitate the most reliable survey using the right tools, processes and interpretation of results to accurately identify the underground utilities within your site area.
Employing accredited and trained experts to complete the Subsurface Utility Engineering process is almost always faster, safer and more accurate and cost-effective than trying to do it yourself.
Tasking the job to site staff who may have only minimal knowledge, training, experience and no formal certification can put your project at risk.
GPR signals reflect when there is a change in the medium. Therefore, it’s able to tell the changes in the soil layer, strata, water table and the approximate depth of the underground layer.
Estimation of ground structure can also be made depending on the signal strength shown on GPR. Normally, the better the signal shown, the lower relative permittivity it is, e.g. dry sand. The worse the signal, the high relative permittivity it is, e.g. clay, saturated sand. However, the estimation can only be used as a reference because GPR signal varies in different conditions.
In terms of locating cable, the maximum depth of scanning depends on the maximum current induced to the utility. According to RD7100 Locator Specification provided by Radio Detection, the maximum depth readout is 30m for pipe/cable and 19.5m for sonde. In practical conditions, we are confident to locate services within 10m and a higher accuracy within 5m deep.
In terms of GPR, the maximum depth of scanning depends on GPR antenna frequency and ground condition. The lower the frequency, the deeper the possible depth it can reach. According to GSSI specification, the maximum depth of a 300MHz antenna is 7m in normal ground conditions. However, the penetration strength varies in different ground conditions.
Which means if you set up a 7m maximum in GPR scanning in clay and cannot see anything at this 7m depth, it does not necessarily mean there is nothing there. It may simply indicate the penetrating strength is not strong enough at this depth to reflect a signal.
Practically, in terms of Service locating, we are confident to locate services within 4m in sand and 2m in clay using GPR. If there is a high-density layer on the ground surface – for example, concrete, bitumen or brick – a significant drop of maximum depth is expected, as signal strength is greatly reduced by these materials.
It is best to obtain a site risk assessment from an expert accredited resource to match your construction activity to the utility risk and requirements under the Australian Standards AS5488.
We generally locate utilities in Quality Level A (Pothole) or Quality Level B (Line locate).
According to AS5488-2019, Quality Level A is within horizontal and vertical accuracy of ±50mm and Quality Level B is within ±300mm horizontal and ±500mm vertical accuracy.
In some condition such as locating drainage, we may provide Quality Level C locating from manhole to manhole. For more Quality Level details, please refer to AS5488-2019 “Classification of Subsurface Utility Information” (SUI).
In terms of Cable Locating, according to the specifications provided by Radio Detection, the locating accuracy is ± 5% of depth, depth measurement precision is ± 3%.
Practically, the accuracy can be affected by induced current and interference of nearby Services.
Overall, the accuracy is approximately within the tolerance range of Quality Level B, ±300mm horizontally and ±500mm vertically.
In terms of GPR accuracy, it’s highly dependent on the ground condition. There is no specific accuracy provided by the manufacturer. GPR generally has a higher horizontal accuracy but a lower vertical accuracy than cable locator as there is not much signal interference in GPR.
However, vertical depth shown in GPR is highly contingent on user setting in soil dielectric, which is normally an estimation made by the technician on site.
It is not likely to get an exact dielectric as it is a changing value affected by different soil composition.
In most situations, the accuracy would be within ±500mm which is within Quality Level B tolerance. However, GPR itself can only tell whether there is an underground object present in the vicinity, but cannot identify what kind of object it is.
Therefore, it is always recommended to use one or more locating method together instead of GPR on its own.
Yes, your Abaxa Technician will undertake a work plan assessment, and document a detailed ‘As Located Plan” or “Survey Plan” corresponding to the scope of work, excavation clearance area on your project. The report will feature a full Utility Checklist to AS5488, risk assessment with tolerances, field diary, safety record, utility permits and associated images. This will be quality checked and then sent to you by our offices within a few business hours of the completed project.
Yes, it can to a certain degree. GPR transmits electromagnetic waves into the ground, and the signal reflects whenever there is a change of medium. A stronger signal reflects high dielectric materials like metal and water and a weaker signal in low dielectric materials like air and PVC.
As long as the object size is large enough for EM wave reflection, GPR can pick up materials such as tree roots, big rocks, buried brick or bitumen, etc.
Even though GPR picks up everything, it does not identify anything.
Because it picks up everything, sometimes it is hard to tell what exactly it is and which one is the target looking for.
Therefore, a GPR scan result reflects combined facets of evidence, assessed with the weight of the technician’s with professional judgement.
GPR transmits electromagnetic waves underground and receives a reflecting signal whenever there is a change of medium. For example, when the signal passes through sand into a concrete conduit, a small portion of the signal will reflect back. When the signal exits the concrete conduit back to the sand layer, there will be another portion of the signal reflected back to convey there is a change of medium.
The EM Wand is a receiver of electromagnetic waves. It can pick up induced objects with different frequency. Normally, a transmitter is used to transmit current to a specific target and induce EM field.
An EM receiver can target specific frequency and locate the target. However, any conductive objects may also be induced in the vicinity if multiple conductive objects are running close together. There will be signal interference as a result which may affect the accuracy of locating.
GPR is a technology that can detect changing medium. While it can be used to find possible objects underground, it cannot identify exactly what these objects are. Objects picked up by GPR are often “unknown” and require multiple instances of evidence and locating methods to confirm what exactly the object is.
GPR can only scan for a line in one sweep. It’s necessary to conduct a full grid in order to get a brief understanding of what is possibly beneath the area.
An Abaxa Technician onsite will normally work out what exactly the client needs and endeavour to satisfy the agreed scope within the allotted time-frame. If a client requests that we locate “all” the Services, it’s categorised as a full investigation – which takes more time than a specific scope.
While a locating method cannot determine if a cable is live, it can induce and track copper cable no matter if it is live or not.
In most conditions, no. GPR works very well when it comes to detecting metallic pipes, is less effective at picking up PVC conduit and highly unlikely to sense optic fibre which is made of glass.
Locating optic fibre inside PVC conduit is similar to locating a gas pipe – and even more difficult in most cases.
However, there may be some factors that make it possible, e.g. good, dry-sand ground condition, optic fibre running inside bigger conduit such as 100PVC – or AC conduit and shallow Service depth.
Theoretically, anything within the scanning range can be picked up. The concrete scanner is a high-frequency GPR which can get a clear resolution even in concrete layers. It can identify reinforcement, Services, voids, etc.
Due to the high frequency of the antenna, the scanning range is normally very small, for example, a 2.6 GHz scanner can scan a maximum 400mm depth in concrete and vary in different condition. If there is high-density reo mesh on top of concrete, it may not be able to pick up anything under the mesh.
Rebar is a steel bar or mesh of steel wires used as a tension device in reinforced concrete. It strengthens and holds concrete tension. Before breaking through a concrete slab, it is helpful to know where the rebar is.
The most effective way to do this is by using Ground Penetrating Radar (GPR) sending signals into the concrete and these, in turn, determine where the rebar is located within the concrete slab.
The exact areas where the rebar is located is marked, and the operator can now proceed safely and effectively to make breaks into concrete, without damaging the reinforcing steel.
A Minimum of 48 hours, typically your work plan will need to be assessed by Engineering and this process may take longer.
Yes it may be possible, but only with ATCO Engineering Assessment and Approval.
In short, no, but in some cases, ATCO engineering may allow a reduction in separation after a detailed consultation and approval to your project construction plan and activity.
No, all ATCO permits must be within their validity dates.
Abaxa’s detailed report and As Located Plan is issued after a quality review within 8 business hours, with faster turnaround available on request. It is important due to the high risk nature of Utility Locating that a cross check is conducted to ensure your project is delivered at the highest quality. If you require a Survey and Utility Survey Plan typically the deliverable will be as agreed or within a few business days.
Yes, on request we can fast track a quality inspection and send over your report.
A vacuum excavator can theoretically extract any material that can pass through the hose diameter within a certain weight range, depending on the suction speed (Sand/limestone spoil/cracker dust road base/small rocks). The vacuum itself is not able to blow material back in. However, we are able to manually tip the material back in and then compact by hand.
Yes, it can vacuum extract water. The volume of water that can be vacuumed depends entirely on the size of the tank. Because of the limited volume of water that can be vacuumed, it can be used to clear water from a manhole or pit, and lower a water table for a few seconds to visually sight objects under the water table, but is not fit for large scale dewatering under the water table.
Yes, we can. However, vacuum trenching for Services without locating the approximate alignment and depth may expend a lot more time than vacuuming within located line marks.
In certain conditions, vacuuming may be the only way to find the Service, e.g. find direct buried optic fibre and non-metallic Services in poor ground conditions. This can be assessed after a thorough investigation and location service, then ways to prove the utilities can be assessed as to the most cost effective way to reduce the risk of damaging the utility on your project.
Optic fibre is not trackable by cable locator and not likely to be visible on GPR. GPR is the only way to locate non-metallic Services. However, GPR effectiveness depends on the condition of the ground. It may not able to locate some Services in poor ground conditions.
In such cases, vacuum trenching in the approximate location is the only way to find the Service. Therefore, it normally takes a longer time to complete jobs with these conditions.
No. While location can be identified, whether it is live or dead cannot be determined by locating method.
While most utilities can be located using a standard digital detector, for some services more specialised equipment is needed. Not all scanners can pick up PVC pipe and other non-metallic materials.
This is another reason why it is extremely important to use accredited professionals, experienced utility engineering professionals to conduct a utility work plan and risk assessment prior to excavation or construction.
The time it takes varies according to the work area, ground conditions, utilities in the area, construction activity and level of quality (AS5488) required at the design or construction stage. It usually aligns with the time estimated by your account manager or if you have a large project the formal estimation process to confirm detailed scope and utility risk assessment, all based on the level of detail provided and the active collaboration with Abaxa to assess what is necessary and critical to ensure your project keep moving without incident. However, there could be changes onsite as a result of traffic conditions, ground conditions, DBYD plan accuracy, number of unexpected ‘unknown’ services, change of scope onsite as investigation develops etc.
Yes, you can but you will not meet the Utility Providers Code of Practice for Western Australia or the individual Utility Providers Duty of Care or the Australian Standards. A plan review is classified as Quality Level D in AS5488 “least accurate level and if used on its own has a high risk of damage”. We recommend Plan, Protect, Pothole and only then Proceed. This involves a full investigation by potholing (Quality Level A) to protect our clients from any possibility of utility damage, you can stage this approach to save time and money which Abaxa can consult on your specific project requirement.
- Pothole removal is the responsibility of the client unless included in the original scope/estimate to remove and reinstate
- Abaxa potholes are valid for the period of the DBYD plans as long as the client protects the work area and markers after our clearance.
- It is recommended the markers be removed when the construction activity is complete and a full reinstatement completed to protect the utility and public.
Common utility services such as electricity, gas, water and communications cable are usually buried at a depth of 200m to 600m beneath the surface. The Utility Providers Code of Practice for WA will detail STANDARD UTILITY SPACE ALLOCATION IN ROAD RESERVES AND LOT ENTRY ARRANGEMENTS and MINIMUM STANDARD OF COVER FOR UNDERGROUND UTILITY SERVICES AND CLEARANCE OF OVERHEAD POWER LINES AND TELECOMMUNICATION CABLES. You can download your copy from here
Contact DBYD in your proposed work area and assess if there are any utilities present, then conduct a visual inspection of your work area for utility indicators including poles, pits and pillars or if your are in an internal property, power lines, bores, sumps, rear garages. Then engage an accredited and trained locating professional to help you investigate, locate and clear your site to the Utility Providers Code of Practise and Duty of Care.
Sometimes pits, manholes and valves are not installed within the required work area. Thus certain services need to be tracked from pits or manholes and traced or backtracked to the required work area.
- Generally, Abaxa locate 5-10m past the clearance area as part of our procedure.
- Access to underground assets could be outside the clearance area (Pits/ Manholes/ Valves / Poles)
- Road crossing services need to be tracked from the source to confirm.
- Incorrect DBYD plans/surface feature not matching with plans, e.g.
- Telstra cable crossing the road from a pit in the other side instead of running parallel.
- Confirm a service does not run into clearance area.
Not always, we may need to investigate many areas to deduct what is planned and cross check all data to confirm what is planned to what is found.
Sometimes an asset owner runs services in their own network, e.g. Optus, NBN, Nextgen and Vocus are not necessarily running in a Telstra network.
Some Telstra distribution does not run through the main pit, so it may not be able to get every Service in one pit.
They are 2 different technologies which have their own constraints.
Locators can only locate conductive Services and GPR can find both conductive and non-conductive objects but cannot identify exactly what they are.
Locators can be used to directly connect or clamp to each trackable Service to identify it. After eliminating conductive Services, non-conductive Services can be detected by GPR in response to evidence like surface features and DBYD plans.
In Australian Standard AS5488, a cable locator is classified as a quality level B locating method. GPR isn’t classified in any of quality levels as yet because it cannot identify Services itself.
In Abaxa, we try to use as many locating methods as we can to make sure all Services in the clearance area are located for our clients. Therefore, both cable locator and GPR are equally important.
Abaxa offers clear and concise reporting of all utility survey results. We offer 3 levels of positive communication
- Physical site marks in paint (or crayon / chalk), pegs, pin tags or pipe (These may be removed depending on preservation of the area)
- Communication with the Site Representative on Investigation and Survey findings
- Detailed Report with Risk Assessment and Plan.
DBYD plans are indicative only. Sometimes services tracked differ from DBYD plans as the locating and designation practise confirms the alignment of all utilities in the work area and scope.
The actual utility survey could differ from what is shown in DBYD plans.
All the information regarding compaction is in the ATCO Additional Information. If you cannot find an answer, the ATCO or APA Approved Supervisor/Permit Officer will try and resolve it on-site by liaising with the Utility Engineering nominated representative.
We recommend you contact your project manager or account manager immediately to discuss the changes, the field technician can document the variation and change in the field diary and will require your signature to approve and authorise the change and associated fees.
No you will require permission to cut or impact any underground asset, to protect yourself and the public contact the Asset Owner to discuss and obtain permission.
There are many accreditations and also years of experience required to be an approved and accredited locator or supervisor in this high risk activity. Please link to our accreditation page to read through the requirements.