Undergruond Utilty Locating Methods and Excavation Law

 

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According to the Common Ground Alliance (CGA) the estimated cost of damage to underground utilities is approximately $30 billion annually. At an average of $4000 repair per underground utility strike this means there are 750,000 underground utility strikers per year. And the most alarming issue is that the large majority if not all of these underground utility strikes could have been prevented if the excavation laws would have been followed. Safe2core is helping mitigate these underground utility strikes  by educating its clients as well as extensively training and educating its Utility Locating Technicians. 

What is excavation? “Excavation” means any operation in which earth, rock, or other

material in the ground is moved, removed, or otherwise displaced by

means of tools, equipment, or explosives in any of the following ways:

grading, trenching, digging, ditching, drilling, augering, tunneling, scraping,

cable or pipe plowing and driving, or any other way.

By law whether you are a homeowner or a contractor it is your responsibility to make sure Underground utilities and underground infrastructure is preserved. Always call 811 and a private utility locating company like Safe2core before you dig!

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There are three standard methods used to perform underground Utility Locating:

Electromagnetic Induction/ Utility Locating

The most used method to locate private utilities is known as electromagnetic utility locating or electromagnetic induction. With this method the utility or tracer wire is induced with a signal from a multifrequency transmitter that can be traced using a multifrequency receiver or “wand” that the underground utility locating technician can use to trace and mark out the centerline of the utility line several hundred feet depending of conductivity and frequency.  This method has a high degree of accuracy but even then, there are some tolerances that should be observed while excavating on top or near a marked Underground Utility Line (to be discussed below). The most common utilities that are traceable by this method are communications lines, gas lines, water, gravity lines, electric lines etc. it is important to keep in mind that this method has some limitations and will not help you locate any non conductive utility lines like plastic lines with not tracing wire, concrete pipes or clay pipes to name a few. That is why it is important to also incorporate Ground Penetrating Radar in all underground utility locating projects. 

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Ground Penetrating Radar

Ground-penetrating radar or GPR is another method for Underground utility locating that is best used as a compliment to Electromagnetic induction or Electromagnetic Utility locating. Safe2core uses both GPR and Electromagnetic Utility Locating on all of its Utility Locate projects.  GPR works by sending a tiny pulse of energy into a material and recording the strength and the time required for the return of any reflected signal. A series of pulses over single area make up what is called a scan. Reflections are produced whenever the energy pulse enters a material with different electrical conduction properties or dielectric permittivity from the material it left. The strength, or amplitude, of the reflection is determined by the contrast in the dielectric constants and conductivities of the two materials. While some of the GPR energy pulse is reflected to the antenna, energy also keeps on traveling through the material until it either dissipates or the GPR control unit has closed its time window. Figure the rate of signal attenuation varies widely and is dependent on the properties of the material through which the pulse is passing. Ground Penetrating Radar can help you close the gap when Electromagnetic Utility Locating falls short when trying to find Underground Storage tanks, Plastic Pipes with no tracers, Concrete and Clay pipes etc.