How GPRS Utility Locating Ensures Safe Excavation

How GPRS Utility Locating Ensures Safe Excavation

An environmental consulting firm called on GPRS to locate utilities prior to the removal of old monitoring wells in Southern California, so they could avoid subsurface damage that would otherwise have derailed the project.

The wells were installed over a decade ago to measure water levels in the ground in 15 locations across San Luis Obispo and Santa Barbara County. Newer wells were installed over the years to replace the ones that were slated for removal, which meant that the old wells weren’t being actively maintained. In some areas, the well covers were buried under asphalt as roads were re-paved.

A GPRS Project Manager operating a ground penetrating radar scanner on grass.
GPRS Project Managers use ground penetrating radar scanners like this one to visualize subsurface infrastructure.

GPRS was asked to locate utilities in a 10’x10’ area around each of the monitoring wells, so that the excavator could avoid costly and potentially dangerous subsurface damage. The average cost of damaging a single buried utility is $56,000, and it typically requires 6-8 weeks of downtime to repair the damage. A utility strike while removing the monitoring wells would have decimated the project’s budget and schedule – and endangered the health and wellbeing of those performing the work.

GPRS’ primary tool for conducting utility locates is ground penetrating radar (GPR), a non-destructive detection and imaging technology that utilizes radio waves to locate anomalies underground or within concrete.

As the GPR scanner moves across the ground or the surface of a concrete slab, it emits radio waves that will interact with any objects – metallic or non-metallic – that they encounter. The scanner takes these interactions and displays them in a readout as hyperbolas varying in size and shape depending on what type of object was located.

When locating underground utilities, suboptimal ground and soil conditions, inclement weather, and the material of the object being located can all limit GPR’s effectiveness. So, GPRS Project Managers (PM) employ electromagnetic (EM) locating in concert with GPR to compensate for this.

GPRS Project Managers use a variety of utility locating equipment.
GPRS Project Managers are trained to use multiple forms of technology when conducting subsurface investigations, to create redundancy and repeatability in our findings.

An EM locator does not locate buried pipes or cables; instead, it detects the electromagnetic signals radiating from these metallic objects.

These signals can be created by the locator’s transmitter applying current to a known pipe, or from current flow in a live electrical cable. They can also result from a conductive pipe acting as an antenna and re-radiating signals from stray electrical fields (detected by the EM locator functioning in Power Mode) and communications transmissions (Radio Mode).

Signals are created by the current flowing from the transmitter which travels along the conductor (line/cable/pipe) and back to the transmitter. The current typically uses a ground to complete the current. A ground stake is used to complete the circuit through the ground.

At GPRS, our PMs are trained and certified in the Subsurface Investigation Methodology (SIM) so they can accurately interpret the findings provided by GPR and EM locating.

SIM is the industry-leading process for conducting utility locates, concrete scans, video (CCTV) pipe inspections, and leak detection. To achieve SIM 101 certification, our PMs complete a minimum of 320 hours of field training and 80 hours of classroom training where they tackle real-world scenarios designed to prepare them for life in the field.

PMs return to GPRS’ state-of-the-art training facility in Sylvania, Ohio during or after their second year as part of our team to hone their skills and receive SIM 201 certification. And they may again return after more time in the field to certify at SIM Level 301 as a Senior Project Manager.

SIM provides a step-by-step process for collecting subsurface data accurately, including a checklist of actions PMs must take to ensure optimal results and the repeatability of our findings. It’s because of SIM that GPRS has achieved and maintains a 99.8%+ rate of accuracy on the over 500,000 utility locating and precision concrete scanning and imaging projects we’ve completed to date.

But the process for accurately locating and mapping utilities begins before we even arrive to your site. We call our field team members Project Managers because they take a collaborative approach to every job, working with you to understand what you need out of our services. We tailor our data delivery method, scope of work, and more to meet your needs and ensure you walk away with information that is both accurate and actionable.

Utility markings on a roadway.
GPRS Located utilities around monitoring wells that were to be removed in Southern California.

In San Luis Obispo and Santa Barbara County, that meant marking the locations of buried utilities and other subsurface anomalies directly on the ground with paint and flags and indicating the approximate depth of these objects where possible. In areas where the well covers had been paved over, we also utilized a magnetometer: an instrument that detects magnetic fields from ferrous, metallic objects. This allowed us to pinpoint the location of these well covers for the environmental consulting firm and establish a 10’x10’ bounding area around those covers within which we located buried utilities.

A Vivax Magnetometer
GPRS Project Managers use the Vivax Magnetometer to detect the magnetic field of a ferromagnetic (high susceptibility to magnetization) object.

With the buried well covers successfully located, and utilities around all the outdated wells accurately identified and mapped, the client was able to complete their work efficiently and safely.

From skyscrapers to sewer lines, GPRS Intelligently Visualizes The Built World® to keep your projects on time, on budget, and safe.

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Frequently Asked Questions

Why is private utility locating important?

According to a report recently published by the Common Ground Alliance (CGA), the direct and indirect costs of damage caused by strikes totaled around $40 billion in 2021 alone, with the privately funded Infrastructure Protection Coalition putting the figure closer to $61 billion.

Over 60% of all buried utility lines are private, meaning they’re owned by individuals or businesses. Hiring a professional private underground utility locating company to identify and map these lines through your project area prior to digging ensures you avoid costly and potentially dangerous subsurface damage.

Does GPRS offer same day private utility locating?

Yes, our professional Project Managers can respond rapidly to emergency same-day private utility locating service calls on your job site.

Will I need to mark out the utilities GPRS locates?

No, GPRS will locate and mark all utilities for you. We have a variety of tools and markers we can use to highlight the locations of utilities, underground storage tanks (USTs), and whatever else may be hiding.