UTILITY LOCATING by ...
Ground Penetrating Radar, Electronic Detection, Vacuum Excavation-Potholing
Ground Penetrating Radar (GPR) has gained significant popularity in the recent decade. Like all other technologies it has its pros and cons. There are also a variety of equipment manufactures but all the equipment uses the same technology at the fundamental level.
GPR works by transmitting an electromagnetic signal into the ground from and antenna mounted on the unit just above the ground surface. As the GPR locator is rolled on its wheels the transmitted signal bounces off the medium back to the antenna where the information is processed real time and the results are displayed on an LCD screen. The results are based on calculations performed by evaluating a time distance relationship.
GPR works great under ideal conditions and is fairly easy to interpret. Under moderate to poor conditions a high level of expertise is required to interpret the results accurately. Ideal conditions for GPR are dry sandy soils; wet and clay type soils produce very poor to no results due to attenuation of the transmitted signal. A good underground utility locating company will not use GPR as the primary instrument of choice for locating conductive utilities because of the knowledge it has on effectiveness, efficiency, susceptibility and accuracy of equipment available.
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Electronic Detection is the most widely used and overall most effective geophysical method of underground utility designation. There are three basis techniques used which are in order of accuracy a) Direct Connect, b) Inductive Coupling, c) Inductive Indirect. There are also a variety of equipment manufactures but all the equipment uses the same technology at the fundamental level.
Direct Connect is the most accurate because if transmits an electrical signal directly through the utility. The following chart provides a good summary of pros and cons for each technique.
The EXARO team has performed underground utility locating by ground penetrating radar all over California; from the bay area to the California Oregon Border South to Santa Ana. This includes all type of facilities from Airports, Hospitals, Electric Transmission & Distribution substations, Gas Plant Terminals, Commercial Facilities, Residential, Public Streets & Highways, Public Transit facilities.
EXARO Technologies Corporation IIPP Guideline G-1006
CGA Best Practices
APWA Uniform Color Code
ANSI Standard Z535.1
Government Code 4216
Gold Shovel (PG&E)
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EXARO - Leading Provider of vacuum excavation-potholing services in California
There are two vacuum excavation-potholing techniques, 1) Air vacuum 2) Hydro vacuum. Like with all techniques, each has it pros and cons. There are also a variety of equipment manufacturers for vacuum excavation; the major differences are the size and power of the units along with the ergonomic and efficiency of the system set-up.
The EXARO Team are experts at Non-Destructive underground utility locating by vacuum excavation. EXARO’s technique of choice is air vacuum excavation-potholing for a couple of reasons; 1) Air is a gas; therefore, compressible creating an air cushion minimizing impact to utility wraps when compared to water. Water is virtually un-compressible which is why it can be used for hydro demolition of concrete. 2) Air allows the use of backfill with native material when desired, especially in those off road locations. Also, air unlike water does not result in mud and potential water run-off which is a big issue in California.
Vacuum excavation is the safest approach to locating underground utilities safety and effectively. Unfortunately many contractors still take a pick and shovel approach to locate underground utilities which carries a high risk of damage simply because pick and shovel are made of steel which make it very easy to damage protective wrap and or simply nick a pipe. The nick of a pipe or protective cover may not result in immediate failure but it certainly is the catalyst for pre-mature failure and catastrophic event. The onset of corrosion due to a nick on a steel pipe is rapid and increases in a non linear format.
Utility Locating: Your best insurance to prevent these type of incidents...