If you’re planning any kind of excavation work, you’ll want to be sure that you’re not going to hit any underground pipes when you break ground. Employing a specialist pipe locating company before you begin is the best way to make sure you’re not at risk of damaging any utility pipes – or facing any hefty repair bills!
Pipe locating in this day and age doesn’t have to be hard, but you do need the right training and equipment to do it successfully. The use of many different materials for pipes, plus the proliferation of other underground utilities like electricity and communications cables means that the days of using a straightforward metal detector are long gone.
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To handle the changing underground infrastructure, today’s pipe locating tools are much more sophisticated than old-school metal detectors. They can identify different cable types and depths to a much more accurate degree. Determining the exact depth and position of a pipe is imperative, both to ensure site safety and reduce delays.
But even with the most up to date technology, it needs a specialist to know when to employ which detection method, and to advise on safe potholing techniques if needed.
Why might you need to locate underground pipes?
Any kind of excavation work comes with the risk of accidentally damaging the underground utility network that provides Australia’s cities and communities with gas, clean water, electricity and telecoms. If you’re breaking the subsurface, you need to know what’s under there.
If you don’t complete the necessary due diligence checks, you could be responsible for cutting off a supply service to a property which may need that line to conduct business. Lines such as gas pipes are used in commercial areas and need to be constantly fed to keep up production. And doing so is likely to see you facing a hefty bill for damages. Potentially one that could take a large chunk out of your liability insurance cover.
What kind of pipes might you need to locate?
You’d be surprised how many types of underground pipes and cables there could be, lurking below the surface of your dig site let alone your front garden. The best way to locate these pipes will depend on the material they are made of and the types of pipe or cable they are.
Some of the common pipes and cables you might need to locate are electricity cables, potable water pipes, sewage pipes, phone lines, and gas pipes. The utility companies that own and maintain these pipes and cables are usually referred to as asset owners. There are several different potential asset owners for each utility type. You’ll need to be able to find out who the asset owners are for any underground services at your dig site.
How do you know if there might be pipes under the excavation site?
The first step is to complete a Dial Before You Dig (DBYD) request. This is a free service that will connect you with the relevant asset owners to get hold of the plans you need to identify any underground services.
You contact DBYD via their website or by calling 1100 (toll-free, during business hours) and let them know the details of your planned project. They will forward the details to any relevant utility owners, who will send you the plans via email – normally within 48 hours. These plans will let you know if there are underground utility pipes and cables located near your dig site.
Of course, this is just the first step. Once you have the plans, you’ll need to have someone competent and experienced to read them. The plans will give you an indication of where any pipes and cables are located, but it’s your responsibility to check their accuracy using appropriate locating methods. You’ll also need to check any additional information or instructions provided by the asset owners.
Make sure you include the DBYD request time into your project planning. It’s important that you don’t break ground before you’ve had the plans and implemented any control measures.
Are there utility pipes under residential properties?
This depends. It’s much more likely in rural areas, but you can never be too sure.
Underground utilities like Telstra main cables are highly likely to be located inside the fence lines of rural properties. Sewer mains that service many properties in a residential area can sometimes be found in the front or backyard of a property, depending on the fall of the land. Even high voltage cables can occasionally be found within your property boundary fence line.
The best way to check initially is to complete a Dial Before You Dig request. This way, you’ll receive an indication of the utilities that might be located within your property boundaries.
For ultimate peace of mind, pipe locating specialists like Geoscope can use highly sensitive locating devices to pinpoint the location and type of any underground utilities on your property.
What kind of technology works best to locate pipes?
Different types of utilities use different kinds of pipes and cables, but they aren’t always made of consistently the same materials. For example, water service pipes are usually made from copper, although more recently, blue brute, poly or plastic materials has also been used more commonly due to the ease of installation and the reduced costs. So, it’s necessary to use a combination of technologies to be sure you’re accurately locating all of the relevant underground services.
If a pipe is made of metal or conductive materials, electromagnetic locating methods are generally considered best practice. By directly connect a transmitter which will induce a traceable electromagnetic field along the pipe.
If the pipe is made of non-conductive materials like plastic, Ground Penetrating Radar (GPR) is often the best method. GPR removes the need to connect to a service with direct connection leads or wires and is not restricted to locating metallic services only. But GPR can also detect various underground structures, including rock, concrete and tree roots and it is the reason we use both pieces of equipment in conjunction when completing our pipe locating search.
Used together, electromagnetic and GPR technology can accurately locate the vast majority of underground utilities.
What’s the benefit of getting a permit to excavate?
That’s why it’s becoming more and more common for construction sites in Sydney and NSW to obtain an excavation permit. By obtaining a permit, you’re making sure that all your excavation works are conducted according to the Code of Practice.
By doing all your due diligence, you’re minimising the risks to your crew members, your budgets and your business by managing all activity undertaken around underground services.
To adhere to the code of practice you’ll need to confirm the actual location of any underground services that DBYD plans and survey drawings show to be within 2 metres of the dig site. You need to do this by either a service location survey or by non destructive excavation/hand digging.
When you know where the pipes are located, you’ll be able to easily manage any risks to site workers and know that you’ve fulfilled your duty of care. A quick discussion and the few minutes to fill in the permit are well worth the peace of mind.
Once you’ve confirmed the location of any pipes on your excavation site, and implemented any necessary control measures, you’re ready to go ahead and dig in confidence.
How does pipe locating equipment work?
Pipe locating equipment consists of two main parts – a transmitter and a receiver. The transmitter sends an electrical signal to the cable or pipe being traced in the form of an electromagnetic field, and the receiver picks up that signal as it is passed over the location in various sweeping passes. This allows the equipment operator to trace the path of the signal and accurately locate the pipe.
The electromagnetic field transmitted by the pipe locator can normally be set to the appropriate frequency, depending on the type of conductor in the cable. These frequencies range from less than 1 kHz to about 480 kHz.
For a copper water pipe in a residential area we find the medium frequency of 33 kHz works really well.
A passive signal is a trace signal on a line which can occur naturally around the pipe or cable, such as the electrical current flowing through an electric supply cable.
As most modern-day locating receivers have a 50 Hz frequency mode built into their systems, it is quite handy in identifying which conductive service could likely be power.
These signals can be used to identify services with a passive sweep using only a receiver. This is normally carried out to locate any inaccessible, abandoned or unknown utilities.
Doing a passive sweep isn’t enough to be sure you’ve located all the underground pipes. Passive signals allow pipes to be located, but don’t allow you to identify the type of utility. The same signal could be transmitted from multiple utilities in the area.
Active signals are generated by a transmitter. With an active sweep, the signal can be applied directly to the utility pipe using the direct connection method. This allows utilities to be properly identified, traced and their indicated depths determined.
The direct connection method involves connecting directly to the target line by using the red and black DC leads with the transmitter. The black lead is ground to earth using a short metal stake and the red lead is connected to the actual pipe wanting to be traced. Once a circuit has been created the electromagnetic current can be through the pipe as well as return through the ground.
For plastic pipes or plastic conduits with copper cables inside such as electricity and Telstra cables, a transmitter ring clamp is applied. The ring clamp is coupled around the service or conduit via the transmitter which sends a signal to the cable without interrupting service to the line. This is normally the best way to locate electric, telephone and internet cables.
Are there any kind of pipes you can’t locate?
Professional locating services can locate all kinds of pipes for you, although some kinds can be very tricky if you don’t have the right equipment, training, or experience.
Sometimes a pipe or cable is inaccessible, and direct connection clips or induction clamps can’t be applied to it, then a general induction sweep must be carried out. This involves placing an antenna on the ground directly above the pipe or cable to induce a signal into it.
While it’s quick and efficient for some utilities, it can be less accurate for anything deeper than 1 metre as the signal might induce into other nearby utilities or lose strength. Reinforced concrete can also reduce the signal being induced with this method.
Non-conductive pipes like pvc and some sewer pipes can’t carry a signal at all.
Locating these involves inserting a detectable duct rod into the line via an access point like a manhole or using GPR.
As you can see, the methods of locating certain types of pipes and cables can be quite complicated! That’s why it’s best to bring in the professionals to make sure it’s done correctly.
How close can underground utilities be to the excavation site before I need control measures?
Each asset owner has a different minimum approach distance requirement. These depend on the type of underground pipe or cable, the location, and the risk involved with the kind of excavation work you are undertaking.
The distance and the control measures can vary greatly. For some high voltage transmission cables, like those owned by Ausgrid, any work within 2 metres of the cable requires an Ausgrid representative on-site to supervise the excavation activity.
Large, high-pressure gas pipelines also have strict exclusion zones anywhere between 2m and 20m. For very high-risk extreme circumstances this distance could be even greater. These measures are necessary to protect their assets and the local communities from the potentially devastating effects of a pipe rupture.
Each asset owner will provide full details of their minimum approach distance along with the DBYD plans. If you have any questions or concerns, you should contact the asset owner directly to discuss them.
Once I’ve had the pipe locations marked using a DBYD Certified Locator, am I ready to start digging?
Why aren’t the DBYD plans 100% accurate?
DBYD plans are a great resource. They give you an excellent starting point to begin the process of locating underground pipes and cables. But there are plenty of pitfalls in relying on the plans alone:
Is pipe locating only necessary for excavation work?
It’s important to locate all underground pipes for any work that penetrates the subsurface. There are various types of work that can cause an accidental utility strike, including the installation of new utilities. It’s not just straightforward excavation or digging that can be a problem.
For example, it’s becoming increasingly common to use Horizontal Directional Drilling (HDD) to install underground utilities. It’s cost effective and removes the need to excavate or open cut trench in built-up areas.
But boring where there are existing services can cause an accidental utility strike. Existing utilities can be parallel to the bore path or even cross under the ground. As such, the same preventative locating measures are needed as with a full excavation.
In addition, it’s extremely important to uncover and window the service so that you can physically see the drilling head pass either under or over the exposed service. The depths recorded by the drilling locator can be influenced by different factors. This means that the only way to be 100% sure the bore w1ill clear the existing underground services is to see it with your own eyes.
Saw cutting is another activity that needs the appropriate due diligence checks completing, before beginning work near underground utilities.
It’s vital that you don’t assume any of the depths and location of underground utilities before you’ve verified them visually.
You may not be able to avoid them completely, but with the correct locating and marking, you’ll be able to implement measures to avoid striking the underground pipes and cables. For example, if you a road sawing the asphalt or footpath and you have a shallow water pipe crossing the area at an indicated 150-200mm below. In this case, you can lift up and over the service and only make a 50mm cut; instead of dropping the whole saw blade through the cut. Little tricks like these can prevent time consuming damages which can halt a site projects progress.
With a little hard work on the jackhammer or bar, the slab can be broken out easily and safely with less risk of busting the water pipe
Why are Geoscope the best choice for pipe locating services in the Sydney area?
Geoscope are the pipe locating service provider of choice in the Sydney area. Our DBYD certified technicians are proficient in the use of electromagnetic radio frequency locators and ground penetrating radar detection methods.
We can locate, identify and mark any underground utilities to the Australian Standard – AS 5488-2013 Classification of Subsurface Utility Information – SUI.
At Geoscope, all our technicians have completed necessary training including DBYD certification and confined space entry and rescue.
We also use the most up to date and reliable technology so that you can be assured of the safety, accuracy, and reliability of our service.
Working with us to locate underground utilities on your excavation site will not only reduce unexpected delays from possible damages but is also proven to reduce design and construction costs.