Underground Asset Location Checklist Before Starting Excavation

By superadmin on December 11, 2018 in Blog

A checklist can help the team become more methodical especially in complex works with irreversible effects (e.g. construction, excavation). With a documented checklist it becomes easier to spot what’s missing and perhaps identify errors later on after the work. It’s also a document that can be improved or modified depending on the job scope and requirements.

It’s especially the case in locating underground assets (e.g. power lines, water pipes, telecommunication cables, storage tanks). Accidentally hitting those assets during excavation or construction can result to major interruptions to the residential and commercial establishments. More importantly, injuries and fatalities might also result if underground utilities were not accounted for early on in the project.

Underground asset location checklist

The checklist starts with specifying the worksite location (including street name, cross street, surrounding structures and landmarks). This location is the area where the subsurface infrastructure should be determined. It’s often the case that surrounding areas are inspected or mapped as well. This way, the team will have complete information about the risks present in the site and surrounds.

For example, more and more Sydney and Newcastle areas are getting more urbanised. The high density of residential and commercial structures often means that there’s a complex network of utilities underground. And yes, pipes and cables often don’t follow a straight path. There are bends and corners which is why mapping underground utilities becomes more challenging.

Even in non-urban areas locating the underground assets is also a challenge. Perhaps the area was an industrial site and storage tanks are still present (which may contain petroleum and volatiles). As a result, it’s important to get the most updated information and learn the history of the site as well.

After specifying the worksite location (and learning its history), the next step then is to use the Dial Before You Dig service. It’s an essential step in any safe excavation. The goal is to protect the country’s network of underground pipes and cables. More importantly, the Dial Before You Dig service is for ensuring the safety of people working near or around those subsurface utilities.

Here’s how it works. First you lodge an enquiry (you specify your worksite location and project information). Then, your info is sent to the relevant asset owners (e.g. Telstra) who are members of the Dial Before You Dig (DBYD). Next is those asset owners will respond and provide you with the plans that would guide you and your team on safe excavation. This also helps in preventing damage to the underground infrastructure.

Failure to do that will expose your crew to hazards (the risks of blind digging). Also, damage to an underground cable or water pipe may cut off essential services to homes and businesses. Aside from being potentially dangerous, this is also very costly because you will be liable for the damages. This also causes project delays that can further increase your project costs (e.g. labour, heavy equipment rental).

In 2014-15, over 1.3 million enquiries were sent to the Dial Before You Dig. Those enquiries were mostly sent by contractors undertaking excavation activities. Whether it’s for developing land for farming, installing or decommissioning utilities or preparing the site for residential or commercial development, there’s always some form of excavation involved. With this activity comes the need to check what lies beneath the ground, which is why the Dial Before You Dig service is crucial in safe excavation.

Having a complete utility map

However, the plans provided by the relevant asset owners (members of Dial Before You Dig) may not be enough. It’s also possible that the information is incomplete or outdated. After all, recent underground installations might have occurred that changed the entire underground network. It’s also possible that utilities were moved or removed. Whichever is the case, updated information and a complete underground utility map are valuable in further improving worksite safety.

So far these are the items in your underground asset location checklist:

  1. Specify your worksite location and project information (e.g. how extensive the excavation will be)
  2. Use the Dial Before You Dig service so relevant asset owners can provide you with the plans

If you want to have a complete and updated utility map, certified Service Locators can help you with that. They can provide you with additional information about the location and depth of all underground cables, pipes and tanks.

Why is this additional step needed? Why not just rely on Dial Before You Dig? First, the asset owners who would contact you are members of DBYD. If one asset owner is missing from their list or that the asset owner failed to contact you, your information about the underground infrastructure is far from complete. Also, remember what we mentioned earlier about the recent changes that might have occurred in the site. Plus, there might be decommissioned or very old underground assets in the area. If the area was an industrial site in the 1960s, there might not be enough records to show that there are underground storage tanks (that may contain diesel and volatiles).

Certified Service Locators use their expertise and specialist tools to pinpoint the location of both old and new underground assets. For example, in locating underground electricity lines professionals use electromagnetic and ground penetrating radar (GPR) technologies. The choice of technology often depends on the nature of the site (e.g. wet or dry soil). Electromagnetic and GPR methods are also being used in locating underground water pipes. The difference is that the choice of technology also depends on the material of the pipe (e.g. GPR can locate both metallic and non-metallic utilities, but must be used in dry soil for accurate results).

It’s a similar case in locating decommissioned underground storage tanks. Old records might not show the exact positions of these or it’s also possible that they were abandoned (and no one bothered to take a record of it). There are dozens of different reasons but whichever is the case, these underground storage tanks can also be located through the GPR method.

The next steps

After the underground assets are located, it’s time to verify the information by exposing them. This is usually accomplished through potholing (digging a test hole to expose the underground utility). Potholing is done with the utility map as the guide (ensure that the test hole gives the easiest access to the utility).

After all those steps, the next thing to do is to create markings so that workers can be extra careful around them (or avoid placing heavy machinery on those areas). Aside from avoiding dangerous areas, the crew would be able to speed up the digging without exposing themselves to risks.

An example scenario

To put it all together, here’s the checklist you can use as a sample reference:

  1. Specify worksite location and gather project information
  2. Lodge an enquiry to Dial Before You Dig and provide project information to the service (asset owners who are members of DBYD will provide you info and plans)
  3. Contact certified Service Locators so you can have more info about the assets underground (some might not be included in the plans provided by member asset owners)
  4. Perform potholing to determine horizontal and vertical location of assets (expose them for certainty)
  5. Provide markings and signages so that everyone will stay safe during excavation

For example, in the construction of the M7 Motorway, it’s important that all the underground assets are located before commencing work. It’s especially the case in the worksite because it has an extensive number of electrical assets. Some high-risk electrical assets were de-energised to make the site safe for work. In addition, only toothless buckets were used in the asset zones to avoid damage to the electrical conduits.

Using the checklist, the entire subsurface asset location included specifying the worksite, gathering and preparing project information, contacting certified Service Locators, performing potholing and providing clear markings and signages. And if possible, some assets should be de-energised or made inactive for excavation to safely commence.

It’s our priority here at One Search Locators to help ensure site safety by identifying the vertical and horizontal locations of underground assets (electrical conduits, power lines, telecommunication cables, sewerage, water pipes, gas lines, storage tanks). We use our expertise and specialist tools so that the resulting markings will be accurate. The complete utility maps we provide also help engineers and project managers better identify the risks in the job site. Contact us today and we can arrive at your site within 24 hours upon your request. We provide fixed rates and ensure accuracy in all our assessments. Our service areas currently include Sydney, Wollongong and Newcastle.