X-ray Vision

X-ray vision isn’t just for superheroes. Underground utility contractors have it too…or maybe the next best thing: Advanced Utility Detection Technology.

Our sub-surface infrastructure is truly a world of its own. A snapshot of a typical urban underground system reveals a complex network of communications, gas, electric, and water/sewer services that originated in the early 20th century. It’s quite a challenge to the crews responsible with its daily maintenance, repair, and upgrades. A construction project, especially in an urban area, is a potential minefield of utilities and objects that can be ruptured, dislodged, or broken by excavator activity.

Contractors must know the locations of these utilities before any construction project begins as contractors can’t risk damaging expensive utilities or endangering their work force. Damaging utilities can be costly, leading to cost overruns and project delays. Records of a site’s underground utilities may be available but unfortunately, utilities and contractors know that there is no reliable paper record. In some parts of the country, utilities are more than 100 years old, and many utilities have been added or abandoned without being recorded. Even abandoned and decommissioned utilities can prove dangerous. For example, an old abandoned natural gas pipeline could have retained significant quantities of flammable methane that could explode upon contact with an excavator bucket.

The construction industry, therefore, heavily relies on various types of underground detection technologies. The technology helps reduce the guesswork and can answer questions like what exactly lies in the subsurface of a job site? Where is it and how deep is it?

Different technologies are required for detecting metal, plastic, concrete pipes, and fiber cables. Products used to locate metal or metallic lines are based on electromagnetic (EM) detection, a technology that has been around for a long time. It is one of the most common and cost-effective techniques. The locating equipment generates an electromagnetic radio signal that is directed onto the utility line. It is used to locate lines that are made of metal or have conductive tracer wire.

The GPR can locate non-metallic material, it often gets used in applications where the previous electromagnetic methods aren’t well suited. These units send out an electromagnetic wave down into the ground; if it hits anything, it sends a signal back in the form of a reflected wave. One of the benefits of this technology is that it makes no distinctions in materials. It finds anything that is down there. This is because GPR reflects off changes in dielectric property between two materials, like between soil and a PVC pipe. It’s extremely valuable when you can’t see what you are looking for.

Potholing, digging holes to locate utilities, is another way to identify buried utilities. It is the most accurate but by far the costliest method. In addition to the high cost of potholing, the poorly or undocumented buried utilities can result in many months of project delay.

Buried infrastructure suffers from “out of sight, out of mind”. A line strike can add thousands of dollars in project costs and can sometimes be dangerous or even deadly. With the aid of advanced utility technology, like the GPR, utility contractors to can “see” what is buried underneath.

Here is an example of a jobsite where GPRS was contacted by an electrical contractor in Dallas, Texas to locate underground utilities prior to directional boring for a new underground electric line. GPRS was able to identify and locate numerous underground utilities including fire waterlines, communication lines, electric lines, sanitary sewer lines, gas lines, and storm drains in the ground and mark them on the surface in order for the client to proceed with their work safely.

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