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When GPRS was tasked with locating and mapping buried utilities prior to the installation of heavy equipment inside a pipeline compressor station in Ohio, we found more – and less – than what the client expected.
Project Manager Matt Higginbotham was originally tasked with locating a single water line running through a 10,000 s.f. area at the station where two heavy pieces of equipment were to be installed. Striking this plastic line while excavating to install the equipment or crushing it under the weight of the structures would have resulted in costly repairs and interruptions to the station’s operations. So, it was vital that the client knew the exact location of the line prior to beginning work.
An existing as-built drawing of the station, however, indicated the possibility of a second water line in the project area. At this point, the client realized they needed a comprehensive understanding of everything buried under the site.
“The customer asked that all potential utilities be located in the area – not just the water line,” Higginbotham said.
Higginbotham deployed both ground penetrating radar (GPR) and electromagnetic (EM) locating to locate and map the buried utilities.
GPR scanners emit radio waves into the ground or a surface such as concrete, then detect the interactions between those waves and any buried objects. These interactions are displayed as hyperbolas on a GPR readout, with each hyperbola varying in size, color and shape depending on what was located. GPRS Project Managers are specially trained to interpret this data to tell you what was located and its approximate depth underground.
EM locators detect the electromagnetic signals radiating from metallic pipes and cables, or from tracer wires attached to non-metallic utilities. The locator’s transmitter can apply a current to the pipe or tracer wire or, if the utility in question is a live electrical cable, detect its current flow. Signals can also result from a conductive pipe acting as an antenna and re-radiating signals from stray electrical fields.
At the compressor station, Higgenbotham was able to verify the location and depth of the plastic water line using his GPR scanner. He then verified his findings with his EM locator.
These same tools helped him locate an electrical ground line in the project area. Higginbotham marked out the location of both utilities on the ground using spray paint, and he used real-time kinematic (RTK) positioning to geo-locate his findings to create up-to-date drawings of the buried infrastructure.
“[Now] the client can safely excavate or shift the locations of the structures for their upcoming project,” Higginbotham said.
The Project Manager also confirmed that there was not a second water line within the 10,000 s.f. zone, despite what the client’s existing as-built records indicated.
“[This suggests] their as-built drawing may be incorrect,” Higginbotham said.
While accurate as-builts are vital for documenting the existing conditions of a building or site, the reality is that your existing as-built drawings are likely out of date or incomplete due to changes that occurred during the initial construction process or later renovations and repairs.
And not knowing what’s below before you dig is the quickest way to cause costly and potentially dangerous utility strikes.
That’s why it’s vital that you hire a professional utility locating company like GPRS to fully map and mark out the utilities in your project area prior to conducting any excavation activities.
Because our client at the compressor station had an accurate understanding of their buried infrastructure before digging, they were able to avoid any unwanted surprises.
From locating buried water lines and electrical cables to documenting entire skyscrapers, GPRS Intelligently Visualizes The Built World® to keep your projects on time, on budget, and safe.
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Frequently Asked Questions
What informational output do I receive when I hire GPRS to conduct a utility locate?
Our Project Managers flag and paint our findings directly on the surface. This method of communication is the most accurate form of marking when excavation is expected to commence within a few days of service.
GPRS also uses real-time kinematic (RTK) positioning to collect data points of findings. We use this data to generate a plan, KMZ file, satellite overlay, or CAD file to permanently preserve results for future use. GPRS does not provide land surveying services. If you need land surveying services, please contact a professional land surveyor. Please contact us to discuss the pricing and marking options your project may require.
Can GPR locate PVC piping and other non-conductive utilities?
GPR scanning is exceptionally effective at locating all types of subsurface materials. There are times when PVC pipes do not provide an adequate signal to ground penetrating radar equipment and can’t be properly located by traditional methods. However, GPRS Project Managers are expertly trained at multiple methods of utility locating.
