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Main Power Line Location
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recent building renovation required mapping the precise location of the main power line entering the building under the slab-on-grade floor. Conquest® 100 ground penetrating radar (GPR) with PCD (Power Cable Detection) provided a quick and easy solution.

Challenges

Many low rise buildings with concrete slab-on-grade floors have poor documentation of utility connections that were placed under the slab. GPR provides a powerful way of mapping out the subslab installations. In this case study, the lead-in from the street to the building was not well defined at the front of the building. The power feed disappeared under the concrete floor and emerged at a panel in the center of the building.

GPR was used to scan the slab-on-grade floor to minimize risk of hitting a power line.

Solution

The contractor selected a Conquest® 100 GPR with PCD (Power Cable Detector) to locate the power cable path. Some of the major benefits of the Conquest include that data can be collected in minutes and, unlike x-ray, little disruption was caused to day-to-day business activity. The added benefit of the integrated PCD sensor is that it can detect live power cables and simplify data analysis.

An initial 8' ×8' Conquest grid was established in a meeting room adjacent to the power panel since this was the probable route for the cable.

The PCD data was collected simultaneously with the GPR data and the results superimposed on a floor plan(Figure 1).

GPR and PCD imaged data
Figure 1:
GPR and PCD imaged data superimposed on building floor plan. The GPR data (left) shows the distribution of the reinforcing in the slab–on–grade. The PCD response (right) shows the classic lozenge-shaped response of a twisted parallel wire.

The GPR data defined the slab reinforcing and gave an indication of a deeper feature. The PCD data was very definitive and clearly showed the presence of the power cable alignment as shown in Figure 1.

With this initial result in hand, a series of smaller grids were run just outside the room in the adjacent hallway. The power line was mapped to the sidewalk outside and tied into the utility street locate marks.

Using the EKKO_Project™ software, multiple grids can be shown together and the user can simultaneously slice through them in depth. In addition, a background image of the floorplan can be inserted, with the data overlaid.

Results

The use of Conquest® 100 GPR with PCD demonstrates the power of combining multi-sensor data to solve a practical day-to-day construction problem. Some key benefits are:

  • Conquest operation is simple and intuitive
  • Users can be effective with only a few hours of training
  • The integrated GPR and PCD provide a high level of confidence in the positioning of live power cables
  • Grid mapping with superposition of depth images on as-built or floor plans simplifies data analysis and reduces poor interpretations

Learn more about Conquest® 100 GPR

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