Importance of Utility Locating
If you are to perform an excavation, you may encounter numerous utilities hidden beneath the ground. You may find a variety of buried water, gas or electric utility lines and communication lines. The possibilities of damaging these underground utilities exist in every excavation site. Having an unexpected “hit” on existing utilities can be dangerous and costly. This could even cause unwanted project delays, service disruptions, repair costs, and potential fines. The only solution for this is prevention; perform utility locating of the site before digging. Anyone digging underground is required by the State’s law to contact the Call Before You Dig service two days prior the proposed excavation, so that utility locating employees can mark lines on the ground. There are different techniques by which utility locating can be done.
Conventional Utility Locating Technique
Radiolocation is the process of using radio waves to find the location of something. Electromagnetic equipment are often used which consisting of a transmitter and a receiver. Electromagnetic signals are often emitted from metal pipes and cables which are detected by the receiver. These signals can be generated by the transmitter and placed on the pipe or it can be naturally occurring low frequency radio waves and electrical noise.
Nonconventional Utility Locating Techniques
Because there are different types of materials used in underground utilities, not all types can be detected with conventional methods. Other types of pipes, such as made of plastic, insulated cast iron, clay or concrete, may require other types of detection and location methods.
Acoustic Locating is the process of using sound to determine the distance and location of something. An acoustic locator is most often used to detect and trace nonmetal water lines. A sound wave is introduced into the water main through a transducer and the acoustic receiver listens for the sound emitted from the pipe. Acoustic locators can also be used in identifying locations of plastic gas lines.
Ground penetrating radar detection is an electromagnetic method that is often used to augment other locating techniques. GPR is a geophysical method that uses radar pulses to image the subsurface. The GPR system consists of an antenna, which contains the transmitter and receiver; and a profiling recorder, which processes the received signal and produces a graphic display of the data. The ground-penetrating radar is able to generate 3D underground images of pipes, power, sewage and water mains.
Magnetic locators or metal detectors and magnetometers are often used to locate buried metal objects other than pipes. They operate by indicating the relative amounts of buried ferrous metals. These are commonly used to locate underground storage tanks (UST), buried manhole covers or any subsurface objects with a large ferrous metal content.
The current technology cannot assure a 100% detection of every underground utility lines and pipes. There are limitations in every utility locating technique that needs to be considered.