Understanding GPR

  • How does GPR work?
    Ground Penetrating Radar (or GPR) works by sending an electromagnetic “pulse” in the microwave band directly into the ground. This “pulse” then is reflected off of objects under the surface and sent back to the antenna and processed by a control unit. The control unit then interprets the reflected “pulses” and provides the technician a visual representation of the reflections. This display is then used to identify targets such as rebar or conduits.
  • What is the difference between your equipment and a crew that can X-ray the floor?
    GPR uses transmitted radio frequencies to locate targets. Radiography (or X-Ray) uses a radiation source to provide an image on a film that is on the opposite side of the concrete. X-Ray requires 2-side access to provide the client an image of the slab. These films that are developed can mistakenly be rotated, flipped or improperly lined up to provide innaccurate target location. GPR is performed live and no processing is required. In addition, because X-Ray uses harmful radiation all work must be performed after hours and a minimum 50′ evacuation must be performed, which includes floors 50′ above and 50′ below from the X-ray. GPR requires NO EVACUATION! With no time spent lining up films, processing films, and no error involved with flipping or rotating films, GPR will scan more holes in a shorter time which saves you TIME & MONEY!
  • Will GPR interfere with my electronic equipment?
    In short, no. All of our Radar equipment is manufactured by GSSI. All GSSI equipment is certified by the United States Federal Communications Commission (FCC). Our GPR equipment and technicians have performed work inside Nuclear Facilities, the Defense Satellite Communications System, and other highly sensitive areas where interference would pose potential interference.
  • How deep can you look into the ground using GPR?**
    Center Frequency Depth of Penetration Typical Applications
    1500 MHz 18 inches Rebar, PT-Cables, Conduit, Voids
    900 MHz 36 inches Deep Rebar Mats, Utilities, Voids
    400 MHz 10 – 15 feet
    Utilities, UST’s, Water Leaks, Grave Locating
    200 MHz 15 – 25 feet Geographical, Engineering, Environmental
    *Penetration depths under good conditions. Actual penetration depths may vary depending on matrix conditions.
  • Will your equipment require additional power requirements?
    No. All of our GPR equipment is operated using batteries specifically designed for our equipment. There are no power requirements required, enabling us to work in the most remote areas.

Capabilities for GPR

  • Can GPR be used to locate unmarked graves?
    Yes! GPR is an excellent form of Non-Destructive Testing (NDT) to locate graves. We are often relied upon to locate both marked and unmarked graves. GPR is a non-invasive tool and we have never had a family member or property manager object to using our equipment over burial plots. We are very respectful when on a site and will leave little to no evidence of scanning a potential grave.
  • Can GPR locate Post-Tension or Pre-Tensioned Cables?
    Yes! On almost a daily basis we are asked to perform this task prior to a concrete cutter core drilling through a slab that contains tension cables. We have performed over 1,000 scans prior to core drilling through a slab that contain tension cables and we have been 100% accurate. GSSI, the manufacturer of our equipment says we have the best locate success of any company using GPR.
  • Can GPR locate PVC conduits prior to me cutting into concrete?
    Yes! GPR is highly sensitive to locating both ferrous and non-ferrous materials within a slab. On a daily basis Construction Solutions technicians are locating conduits in both suspended and slab on grade concrete structures. Our most frequent applications are inside of hospitals and inside grocery stores. Our ability to locate conduits has resulted in hundreds of thousands of dollar savings for our customers.
  • Can GPR determine the presence and severity of corrosion in embedded rebar?
    Yes! Construction Solutions will be able to grid out an area where corrosion is of concern. In a relatively short manner of time we will collect data from EVERY piece of rebar. Using sophisticated software and statistical analysis we will be able to identify where areas of corrosion are occurring and be able to provide quantitative data, correlated with on-site evidence, the extent of the corrosion.
  • Can GPR determine if a buried pipe is metallic or non-metallic?
    Yes! In several applications we have been asked to not just locate, but identify whether a buried pipe is metallic or non-metallic. Many of these applications are at convenience stations where the ability to tear up a gas station and parking lot is not ideal for the client. All of our work can be, and is performed during normal hours of operation with zero interference with the normal course of business.
  • Can GPR be used to locate a water leak underneath the soil?
    Yes! In many applications where evidence of a leak may only be the rising consumption of water on your bill we are able to perform a scan to locate where a water leak is located. GPR is highly sensitive to the dielectric constants of materials. Water’s dielectric constant is so high that it is a very strong reflector. On several occasions we have located water leaks with pinpoint accuracy.
  • Can you locate voids in and below concrete?
    Yes! For various applications Construction Solutions has located voids in and below concrete. In the September/October 2008 Concrete Repair Bulletin, published by the International Concrete Repair Institute, Construction Solutions worked with Structural Engineer Associates, Inc. to locate voids underneath the water fountains at Kauffman Stadium. GPR was able to pinpoint where the voids were and reduced repair costs.
  • Will you be able to tell me the size and volumes of voids?
    GPR on it’s own isn’t accurate enough to determine the exact size of voids. Construction Solutions has been successful at determining relative sizes of voids when able to verify through core drill samples.
  • There is a concern over the depth of cover for the rebar in this structure. Can you identify what areas don’t have the required cover?
    Yes! Using GPR we can map out an entire area and gather exact location of all rebar in a structure. Using information supplied to us we can create a full contour map to identify locations where the depth of cover is out of spec. Please review our case study on Coralville, IA parking garage or Salem Nuclear Plant for greater detail and examples.
  • The inspector was not on site to see the rebar placement prior to pouring concrete, can GPR locate the rebar, determine spacing, and rebar size. Will the inspector accept the information?
    Yes, yes and yes. GPR is fully able to locate rebar and identify exact location in x, y and z-axis. We will also be able to approximate size of rebar and present all information to the inspector. In every circumstance the inspector has always accepted our reports when an inspection was not performed.

GPR specific to Construction Solutions

  • My local one-call service will not locate utilities on our property. Can you locate utilities on private property?
    Yes. For many states there is an 811 service that will locate utilities on public grounds free of charge. That service will only locate on public right-of-way. This includes homeowners and all public grounds. This will not include any utilities on private grounds such as a parking lot for a business. Prior to excavating Construction Solutions will locate all utilities that an 811 service will not locate.
  • I have a job located in _____________. Can Construction Solutions still perform GPR work for me?
    Yes. We place no limitations on where we will travel to perform GPR surveys. This includes all 50 states and any international location. To date we have worked in 36 states and 19 countries.
  • Our job location requires training specific to the jobsite. Are your technicians capable of working in this environment?
    Yes. All of our technicians have undergone various training classes to be able to perform work in almost any environment. We even have workers that are certified to work in Nuclear Facilities. All of our technicians are also required to wear full PPE. Safety on a jobsite remains our highest concern.
  • Many web sites claim that GPR does not work in heavy clay soils. You locate many items such as utilities, graves and UST’s in Kansas and Missouri where heavy clay soils are prevalent. How are you able to locate in these conditions?
    Locating in clay soils is a very difficult task. Construction Solutions is the only GPR company located in the Midwest offering utility locates because of our ability to successfully use GPR in clay soils. Our exact methods of locating Utilities is a result of many years of experience of scanning in these conditions.
  • I have several people in my office that would benefit from your services. Are you able to present on-site demonstrations?
    Yes. We would gladly visit you at your office or at a jobsite to present to you our capabilities. Please call us today to set up your presentation.
  • Why is Construction Solutions my best choice for using GPR?
    There isn’t anything we haven’t done with GPR. Our success rate is so high that even the manufacturer is astonished at our capabilities. Since our focus is entirely centered around GPR we have developed techniques and used previous experiences to continue our success with GPR. When 95% of all of our new business is created by referrals we know we are meeting our customers expectations. When you need to know, use Construction Solutions.