Concrete Structure Scanning is the method of accurately determining the whereabouts of utilities, post-tension cables, objects or features buried inside and under concrete structures.
It requires the use of technology specifically designed for the purpose. This specialized equipment is High-frequency/High-resolution Ground Penetrating Radar which must be operated by qualified technicians following strict scanning procedures. Utility Survey Corp.’s 10-Step Concrete Structure Scanning Protocol™ sets the standard for this. The concrete scanning technician will mark the position of all detected utilities, post-tension cables, objects, and features on the surface of the slab with color-coded paint or chalk.
The choice of a marking medium will depend on the job-site conditions (ie paint for the marks if some degree of permanence is required, or, chalk if for aesthetic reasons marks are not permitted to remain in place). The color-codes must conform to industry standards.
“Concrete Scanning” is a very general description. It is probably the most commonly used term but there are also several others – which can be confusing. The following will explain these terms and help you be clear about what you should expect to be getting when asking for a Concrete Scanning Survey.
Ground Penetrating Radar (GPR) is the most versatile, cost effective, safest, and most widely used technology for “seeing” into and through concrete structures.
Typical terms for concrete structure scanning with GPR are: “Ground Penetrating Radar Scan” or “GPR Scan” or, “Radar Survey”.
Most concrete structure scanning surveys could be satisfactorily accomplished solely with the use of Ground Penetrating Radar (provided the appropriate systems and corresponding antennas are used). However, in the interests of safety, to help detect the presence of live electric wires buried in a slab, Utility Survey Corp.’s 10-Step Concrete Structure Scanning Protocol™ also requires that EM/RF locators be deployed.
“X-raying” is what prospective clients typically confuse with Ground Penetrating Radar. There are three significant reasons why Ground Penetrating Radar is the preferred choice over X-raying for concrete scanning:
1. More versatile: Ground Penetrating Radar is more versatile than X-raying. GPR only needs single-side access to a structure whereas an X-ray setup requires access to two directly opposing sides. And this is not always possible.
2. Safer: Ground Penetrating Radar is safer than X-raying. GPR doesn’t generate the harmful radiation that X-raying does. The radiation being given off by x-rays creates a hazardous work environment which means a large radius around the work area has to be cleared and cordoned-off before scanning can begin. This is not always possible or convenient.
3. Less expensive: Ground Penetrating Radar is a much more cost effective alternative to X-raying.
“Utility Locating” is also often referred to as a “Locate” or a “Markout”. However, none of these three descriptions calls for, or implies, any specific methodology or the use of any particular piece of equipment. And that could result in two particular problems occurring for the unwary:
1. The client doesn’t fully understand what it is exactly he or she will be getting. Asking for a “slab markout” won’t guarantee someone will have the right equipment do the job. They could believe they will be getting a comprehensive concrete scanning service when in fact they’re not – and that could lead to something really bad happening.
2. An apples-for-apples service provider comparison is impossible because there isn’t enough information with which to make a comparison. This could lead to someone showing up to do a job they’re not equipped for, trained for, or capable of doing in the way a professional concrete scanning project should be carried out. This could also result in a bad outcome.
The term “Scanning” is about as close as it gets to a reasonable description when the client understands they need a thorough, professional, concrete scanning service.
However, the question, “Scan with what?” isn’t usually covered or thought out. And, that’s a very important omission. Just asking for Ground Penetrating Radar isn’t enough. Scanning with the correct GPR system and most suitable high-resolution antenna frequency configuration is what’s important and something the client should be clear about.
A comprehensive concrete “Scan” should be, and can only be carried out effectively by using Ground Penetrating Radar systems that are correctly configured for the job – and which must be operated by professional technicians who are trained, skilled, and experienced in their use.
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National Utility Locating Contractors Association