How to Locate Underground Cables & Ensure Safe Digging

How to locate underground cables? Commonly, professionals find an access point and inject an electrical signal onto the cable. Then they trace the signal’s path which thereby provides a map of the underground cable.

It’s a basic technology that has been used for decades. However, the tools and methods might have evolved through the years. That’s why many construction and excavation firms hire professional locators to ensure safety before digging.

Why locate cables underground before digging?

Before the backhoe breaks up the earth, all the underground power lines should be located first. This is to prevent accidents, injuries and power interruptions to the community. Accidental impact to the cable may cause the following:

  • Electrocution and injuries (or fatalities) to workers on site
  • Damage to the electrical and telecommunication cables
  • Power or telecommunication service interruption to the residents and businesses
  • Project delays because of temporary halt
  • Additional costs and legal fines

Back then old records might suffice in locating the few subsurface cables. But now complex networks of subsurface utilities exist. In a modern society you’ll likely find varying cables and pipes underground. Not all of them are active but still it’s ideal to locate all cables to ensure safety.

The cables might be tangled or there are areas where there’s a high density of cables and wires. There are also areas where there are very few cables installed underground. Whichever is the case, the location of all the cables (and pipes) should be pinpointed to prevent workplace accidents and project delays.

Why hire professionals for the job?

As mentioned earlier, there are now modern tools and methods for detecting cables underground. These require expertise because technology is only as good as how it’s used.

For instance, setting the transmitter to a specific frequency requires a working knowledge of the types of conductors and cables underground. The wrong choice of frequency might result to erroneous results (the signal might bleed out and generate unusable data).

Selecting a frequency (e.g. 1 kHz to 480 kHz) can be a tedious and slow process. Some professionals start with the lower frequencies and then gradually choose the higher ones. Experienced locators on the other hand might already have familiarity with the project type. They can set the right frequency after just a few tries.

Aside from proper choice of frequency, certified Service Locators also consider the following things:

  • How to get the signal onto the cable (finding and using an access point)
  • Which method to choose when sending the signal (e.g. direct, general induction, inductive coupling)
  • Estimating the depth of the cables (the location including the depth is crucial)
  • Timeline of the project (utility maps should be available as soon as possible so the project can commence)
  • Interpreting and verifying the data gathered

Additional measures might be taken depending on the scope of the project and the complexity of the subsurface utilities. Professional locators are also likely to locate underground pipes to further add to the workplace safety.

From the first step (locating and using an access point) up to the interpretation and verification of the data, certified Service Locators are careful to which method to apply. For instance, getting the signal onto the cable may require any of the following methods:

  • Direct connect
  • General induction
  • Inductive coupling

Directly connecting the transmitter (physically attaching the transmitter to the cable) only requires an access point. But in many cases, the cable might not be accessible or almost impossible to locate at first. That’s why locators might use either general induction or inductive coupling to send the signal.

General induction works by inducing a signal (through the use of magnetic field) in the cables under. The target cable may pick up the signal and then the tracing begins. However, nearby conductors may also be “induced.” After all, it’s an indirect method and there’s no guarantee which object is picking up the signal.

There’s another method which is inductive coupling. It’s more accurate and reliable because a coupling device surrounds the cable. The device then emits the electrical signal and tracing commences. However, you need an access point for this method to work.

Direct-connect and inductive coupling are similar because they require physical access to the electrical cable. The difference is that the latter induces an electrical signal (“activates” the line) which can then produce a further trace or path.

Special concerns when locating buried cables

Historical records and old marks are not enough to pinpoint the buried cables and proceed with the excavation. Often, these records are already outdated because additional cables might have already installed. It’s also possible that these cables have shifted naturally or artificially.

Whichever is the case, you need the most recent information regarding the location of the buried cables. This is accomplished by allowing a certified Service Locator to assess the site. Although many professional locators still use old records, they use them for initial reference and starting points. These old records are guides so locators will have an idea about the characteristics of a site.

As stated earlier, underground cables actually form a complex network. For excavation and new construction projects, all these cables (including the pipes and underground storage tanks) must be located. Some projects require though that only specific cables should be located for maintenance, repair, upgrade or inspection.

What happens when underground cables are forgotten

First, there are safety risks associated with blind digging. Many of the subsurface infrastructures might be located 1.5 metres below the surface. It’s possible that within a few minutes of backhoe operation (or manual excavation) someone will hit an electrical cable. The cable might be damaged through either of the following:

  • Cable was cut through by a sharp object (the point of a shovel or other digging tools)
  • Cables were crushed by a heavy object (land and debris) or a backhoe (was placed just over a cable)

It’s especially the case when using powerful equipment. Its force might be difficult to control thereby making the damages far worse. As a result, the damage may lead to the following scenarios:

  • Electrocution of nearby workers
  • Mild electrical shock that might result to a fall or bump to the head
  • The backhoe might hit the water pipes and amplify the electrical hazards

Aside from safety risks, damages to the subsurface electrical cables are also likely to happen. These will result to the following events:

  • Temporary halt of the project to prevent further dangers
  • Analysis of the site (determine the present and future sources of hazards)
  • Partial or total destruction of the electrical cables
  • Legal fines and interruption to the community
  • Delays that would result to additional project costs
  • Rework and possible redesign of the whole work plan

In other words, blind digging is dangerous and possibly very costly on the part of the property developer. Whether it’s digging for trenches, holes or foundations, the risks are always present if there’s incomplete or inaccurate information. After all, underground cables may appear harmless (often appears like dirt or a pipe). But when a machine or someone hits it, the dangers would affect the workers and the whole project.

Safety during emergency excavation

For normal excavation projects, utility mapping is crucial to avoid dangers and hazards. It’s also the case with emergency excavation. There might be live buried services in the area which might cause more damages and injuries.

High-voltage cables might cause electrocutions and fires if the excavation was not planned properly. In any case, it’s safe to assume that there are always live buried services in the area. These can be successfully avoided if there are accurate and updated utility maps in the first place.

As much as possible, excavation may start with trial holes to initially confirm the location of underground cables. Throughout the excavation process, safety is always observed. It’s also possible that locators intermittently (or continuously) detect the cables to confirm their locations. This is to account for any possible positional changes of the cables during excavation.

How to locate underground cables

Certified Service Locators use electromagnetic equipment to send signals onto the power lines and interpret those signals upon their return. This results to a map which can be used as a guide for engineers and crew when digging or before planning any excavation work.

With an accurate and updated subsurface utility map, the crew could then avoid damaging or tampering the buried cables. This results to improved safety and faster project progress. That’s why many developers and engineers often rely on certified Service Locators for the job.

Here at One Search Locators, we specialise on accurate detection and mapping of subsurface utilities. We use electromagnetic equipment and other modern tools to ensure accuracy. Our expert team have already handled dozens and hundreds of projects for different commercial clients in Sydney, Melbourne, Newcastle, Wollongong and surrounding areas.

Contact us today and our team will arrive on your site within 24 hours. Our certified Service Locators will focus on your requirements to successfully complete the job. We can provide you with a free quote for locating all underground utilities in your site.

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