Trinity Christian School Utility Mapping
Finding the needle in a haystack, so that our customer
can dig in exactly the right spot to hit their target.
Two Impossible Targets, Two Victories
A representative of GoRapid Plumbing reached out to Bigman Geophysical with a project that required mapping water and sewer lines at Trinity Christian School in Sharpsburg, GA. The project had hit a hitch when they discovered that no as-built information for the school’s sewer system existed, and theories about the utility locations had proven wildly inaccurate. In order to repair and maintain the damaged sewer systems, GoRapid needed to follow lines and map out key parts of the network, so they could determine where failures had occurred. Other companies had been called to the site previously, but the quantity of underground pipe signatures far outweighed the number of surface features that could be tied onto with traditional pipe locating techniques, and there were so many signatures that traditional push-and paint GPR techniques had proven minimally effective.
The school was fully operational, and it would be tremendously cost-prohibitive and imposing to the function of the school to do sample excavations to expose the pipe network, as that would require shutting down the primary access rout to school buses that moved thousands of students. Bigman Geophysical was tasked on rapidly finding a key pipe intersection that needed a cleanout installed immediately to solve a sewage line failure, and they would need to map a network of pipes in an area near the athletic fields.
Project Metrics
Target A: Intersection of Two "Undetectable" Pipes
The assigned project manager and field team deployed to the site with a Proceq GS8000 ground-penetrating radar system, and met the GoRapid representative on site near target A. It became immediately apparent that the subsurface environment was heavily disturbed by construction, and that there were numerous unrelated features that were complicating the ability to follow signatures with EM Locator devices, due to signal jump. Since there was no above-ground feature outside of the building that could be attached to for an induction clamp, or used to identify the correct pipe and follow it, traditional techniques were unlikely to succeed. Using the advanced system and years of training, however, the operator on site made quick work of the project using the freepath mode with an integrated SRS GPS system to map all of the features near the target, and narrow down targets by intersections. It was found that only one intersection was present that could functionally tie in the affected lines, and so this point was flagged on the surface for excavation. The operator then moved on to area B.
The target intersection was clearly identified despite a complex subsurface environment with dozens of other nearby features. The location was immediately marked for excavation.
Target B: Spaghetti Junction
The second area was near an athletic field, where an unknown number of features converged toward an access point, but lack of a proper map had invalidated previous attempts to differentiate the many features involved, as signals sent from the surface were far too likely to jump from one pipe to another, and other GPR operators had likewise found the shear volume of reflection signatures prevented the usual method of following each target and mapping them one at a time; the environment was simply too dense for normal procedures.
Bigman Geophysical decided that the right tool for the job was to grid the area with bi-directional scanning pattern, at 18" intervals, and use computer software to model the responses with a much higher degree of certainty. The operator spent less than two hours on site carefully pushing the equipment in a grid pattern, aided by the integrated GPS, which allowed them to go around features on the surface and produce a tightly fit scan that hugged the boundaries of the surveyable area.
Bigman Geophysical was on site for a half-day of work, and the remote processing team spent one full day analyzing data, drawing targets in a 3D volume, and writing a summary report. The flagged pipe intersection was exactly on target and the deliverables proved to be highly accurate and directly actionable to GoRapid. The customer was able to move forward with repair work at the school without further delay.
Results Slideshow
