FAQ

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
1600 MHz	18 inches	Core Drills & Other Near Surface Investigations Needing Finer Detail
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 contains 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 Echo GPR Services 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! Echo GPR Services 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 Echo GPR Services has located voids in and below concrete. In the September/October 2008 Concrete Repair Bulletin, published by the International Concrete Repair Institute, Echo GPR Services 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. Echo GPR Services 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 Echo GPR Services

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 Echo GPR Services will locate all utilities that an 811 service will not locate.

I have a job located in _____________. Can Echo GPR Services 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 websites 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. Echo GPR Services 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 Echo GPR Services 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 Echo GPR Services.

Concrete Scanning & GPR

How accurate is ground penetrating radar?

Our Certified GPR Operators will regularly locate rebar, post tension, and conduits within concrete with 1/8” accuracy in x and y directions. Depths to targets are accurate to within 10% of depth.

Can ground penetrating radar identify the difference between rebar, post tension, and conduits?

While GPR equipment on its own is not capable of differentiating embedments, our highly trained and certified operators have the skills needed to look at the scans and identify the differences.

Can ground penetrating radar scan one-side-access?

Absolutely! The benefit of using Concrete GPR over Concrete X-ray is only 1-side access is required to image through concrete. Our versatile and ergonomic Concrete GPR scanner can scan up to 24 inches into concrete floors, walls and ceilings. In some limited circumstances GPR may require 2 sided access and our expert GPR Project Managers will educate you on those limited situations.

Are your GPR technicians certified?

YES! Echo GPR employs CSDA-certified operators to perform your GPR surveys. The Concrete Sawing and Drilling Association (CSDA) offers the only GPR Certification in North America. While other companies tout “certified”, it is a certification that is issued in-house, not from an outside source. As the only Accredited and Certified GPR company in the Midwest Region our knowledge of Ground Penetrating Radar and its application in concrete scanning is unmatched.

Our long-standing, proven success and dedicated approach to marking out a jobsite has been used as the foundation for creating the GPR industry’s only Best Practice for marking out Concrete Embedments (CSDA-BP-017).

What is the difference between concrete GPR and concrete X-ray?

Ground Penetrating Radar uses a radar signal to transmit a signal into the concrete and measure the reflection of the returned signal. This allows for 1-side access in most applications. Concrete X-ray however uses a radiation source and requires both a source and film to be on opposing sides of the concrete, requiring 2-side access. It also prevents the use of X-Ray in slab-on-grade applications. Both technologies are capable of scanning through suspended concrete; however, GPR does not interfere with daily operations. Using X-Ray to scan concrete requires evacuation of the work area.

Utility Locates

Why won't One-Call locate all of my utilities?

Public Services, by law, are required to provide utility locates for the portion of the utility that they own. This typically means up to their meter in most situations. Beyond that the utilities are privately owned. One-Call legally cannot locate these utilities, that is where Echo GPR Services steps in. Our field professionals will locate private utilities including those utilities that are even inside your building!

Can Echo GPR provide me with a map of all the utilities that were found?

Yes! This is a service that is not normally required, but at your request, we can provide maps of utilities found on your site at varying degrees of accuracy. If you require survey grade accuracy, we partner closely with some of Kansas City’s best Professional Land Surveyors to subcontract under us to provide you with as detailed of a drawing as you require.

Can ground penetrating radar locate all of my utilities?

GPR can provide you with the ability to locate utilities not capable of being located by traditional EM locators. GPR’s ability to fulfill some of the limitations of EM makes it a useful tool in locating utilities. However, all sensing-type equipment has limitations in different environments.

Our GPR professionals at Echo GPR will work to locate all utilities capable of being located with sensing technologies.

Can ground penetrating radar identify my utilities?

Normally, GPR on its own cannot identify a type of utility. The use of GRP, EM, and other utility locating equipment is used parallel to each other to help identify utilities. Existing drawings are also useful in determining what utilities are found. However, utilities that have been abandoned underground can pose difficulty in identifying them. Our onsite professionals will communicate all found anomalies on a site to aid you in your underground efforts.

Other than ground penetrating radar, what other technologies does Echo GPR employ to locate utilities?

Beyond GPR, Echo GPR uses traditional EM locators that utilize transmitters and receivers. Additionally, all of our GPR professionals are equipped with Duct Rodders for inserting a traceable wire into accessible utilities. Most importantly, our technicians are experienced in utility locating, with hundreds of hours of training, and will work to problem solve any specific difficulties in finding utilities underground.

Pre-Site Investigations

What is a pre-site investigation and why do I need it?

In it's most simple explanation, a pre-site investigation is detecting disturbances underground that are not consistent with the surrounding soils. The mapping of a site can specifically direct soil borings to discover what is underground.

How much does it cost to perform a pre-site investigation?

This is determined by a variety of factors. Each site will provide its own characteristics, mainly size, and site conditions. The Echo GPR team of estimators will work with you to provide you with a cost-free estimate of your project. Generally, in the scope of an entire project the costs of a pre-site investigation are minimal, usually less than 0.05% of a project’s total cost.

What are the things that GPR and EM can detect in a pre-site investigation?

Our technologies have uncovered a wide range of buried items. These include:
• Building Foundations
• Underground Storage Tanks
• Building Debris and Backfill
• Filled-in Ponds
• Tunnels
• Septic Tanks
• Abandoned Boilers
• Storm Shelters
• Gravesites
• Even an old vehicle and washer and dryer!

If my site has always been vacant, why would a scan need to be performed?

Even the most innocuous sites have revealed unknown anomalies. In rural settings these include buried 55-gallon drums, t-posts, fencing material and old burn piles. In more urban settings we often discover long forgotten building foundations left when a building was demolished. Even discovering inconsistent backfill can be useful in planning for the excavation and or grading plans of a site development.

Locating Voids and Sinkholes

Road and Bridge Inspections

What information can GPR provide for Bridge Inspections?

GPR is an effective tool for providing information regarding bridge condition such as rebar corrosion, delaminations, depth of cover and even provide engineers a look into how the reinforcement is placed within the concrete, revealing information that may not currently be accessible.

Are there any industry specifications or standards that you follow?

Absolutely. Echo GPR follows ASTM Standards in providing GPR services in the Road and Bridge industry.

ASTM D4748 / ACI 117 for the Evaluation of Bound Pavement Thicknesses
ASTM D6087 for the Evaluation of Asphalt-Covered Bridge Decks for Rebar Amplitude Mapping
ASTM D6432 for using GPR as a Subsurface Investigation Tool

Is your GPR system pushcart or vehicle mounted? How fast can you scan a bridge?

Both! However, using large multi-channel (arrayed) GPR systems expedite the speed in which we can scan a bridge deck and greatly multiplies the amount of data we get. A push cart system is typically utilized in smaller and rural decks where time to scan and lane control needs are greatly reduced.

To get the most detailed scans we use a ground coupled system that can collect between 15-20 mph. This super hi-resolution system will get full 3D imagery and allow us to process data in accordance with ASTM D6087
On larger, broader scale projects we can use our air-coupled systems and collect up to 75mph or the speed limit on any highway. Not as hi-resolution as a ground coupled system, it is extremely effective at providing depth of cover information such as pavement thickness in accordance with ASTM D4748 / ACI 117

What type of deliverable can I expect?

Getting the most out of a report in a concise and easy to understand deliverable is one of the most important things we can do at Echo GPR. Upon data collection of the project our deliverables consist of the following:

Written report of GPR scan and summary of findings
Plan view GPS coordinate color contour map showing deterioration and delamination
Statistical summary of rebar amplitude map
High resolution video of deck time stamped to GPR data
Asphalt overlay thickness (where applicable)
Concrete cover over rebar (where applicable)