GPR Case Study 2 – Utility Locating – Hanover Engineering

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hanoverGPR - Ground Penetrating Radar - Utility Locating

When Hanover Engineering began work on a 20-mile long sewer project estimated at $18 million, they knew it wouldn't be easy to analyze the subsurface rock on the trench lines. Traditionally, this task would require boring test holes approximately every 30 feet--a tedious, time-consuming approach that's still regularly followed. If the project's team had stuck with this approach, more than 3,500 holes would have to be bored for analysis.

But Hanover Engineering, an East Coast firm providing consulting, civil engineering and support surveying services, did not have the time needed to bore that many holes. The project's timeline was restricted by a grant, and so there was nothing for it but to search for a faster, more modern method to accomplish the work.

"I felt we needed to find some type of system, some type of equipment, that could survey in a way that we could analyze the amount of rock on these trench lines," said Matthew Epler, EIT with Hanover's Ephrata, Pa., office.

The firm's research found the wheel-mounted Seeker SPR (sub-surface penetrating radar) from US Radar. This equipment turned the project into a walk in a trench-lined park. Crews pushed the Seeker over the surface of the trench area, relying on its sub-surface penetrating radar system to do the work for them and then display the results on the touch screen panel.

"We have survey data on 20 miles of pipe," Epler said. "I have all these scans and all these pictures (from the Seeker SPR)." Epler estimates the Seeker SPR decreased the time needed to survey the area by 70 percent. Plus, it diminished any environmental impact concerns that might accompany a project typically requiring thousands of bore holes to confirm the data the Seeker has provided.

The Seeker is technologically advanced and yet simple to operate and easy to maneuver. It transmits energy pulses through various types of surfaces, including clay, soil, concrete and brick. Whether the depth range being explored is known or not, the Seeker produces images of what's below and can tailor the picture based on a user's set parameters, such as soil settings algorithms, and color palette. Everything is displayed immediately on a large, bright screen that's easily visible even in daylight. "It's like looking at an x-ray," Epler said. "The more you look, the more you see."

The 500-megahertz antenna that Hanover chose for their unit is among the most popular of the frequency options US Radar offers. The full range extends from 100 to 2000 Mhz. At 100 megahertz, the Seeker SPR works best for detecting sizable objects, such as bedrock and large pipes, at depths of up to 100 feet. The 2,000 Mhz antenna provides high-resolution details at depths to 19 inches, displaying everything from fine wire to cracks in concrete. Hanover's 500 Mhz antenna provides good versatility, with up to 14 feet of detection for pipes, cables, and soil disturbances.

Beyond the sewer pipe project, Hanover anticipates its Seeker SPR will be beneficial in other engineering applications such as finding sinkholes or locating storm pipes for clients. Hanover has already used it to locate water lines and water services and to explore tight spaces to avoid conflicts between existing and proposed utilities. The company is also interested in exploring GPS options with the Seeker, which can be attached to an external GPS device for additional data collection.

"The GPS option is one we're very interested in and one we'd get a good amount of use from," Epler said. "It can tell us exactly where we're at, where the scans start and where they stop. This would be a time-saving feature and just help make the process more precise."

More than 50,000 lineal feet of data can be collected and stored in the Seeker before it is transferred via a USB port to a Windows-based operating system that processes and filters the information. Additional software allows for even greater processing capabilities, although the basic acquisition software that comes with the equipment handles many needs.

While "computer data syncing" and "rugged" don't typically go hand-in-hand, that's not the case with the Seeker SPR. All of the machine's cables and connections have been constructed with tough, military-specification, waterproof connectors. Two sturdy wheels balance the equipment for stability, which also minimizes the pushing effort and, consequently, operator fatigue. An optional rough terrain attachment with two additional tires makes the machine ready to traverse almost any surface condition.

The Seeker provides an accurate, real-time picture of what lies beneath--whether it be wires, bedrock or large pipes--all without disturbing the surface or consiming valuable time as is the case with more tedious methods. Plus, it does so silently by operating off of a battery that provides four to six hours of continuous run time.

"I would honestly go as far as saying this equipment is a survey tool," Epler said. Obviously it's not the answer to everything, as no one piece of equipment is, but it's a very good survey tool to have in the toolbox."