A power generation plant in Sandwich, Massachusetts, believed they had a leaking utility line on their property.
But they didn’t know where the leak was – or what exactly was leaking.
Plant officials detected evidence of the leaking utility with a thermal imaging camera, however, this was not enough data to pinpoint the source. The problem was that the leaking line was encased in what was most likely a concrete or asbestos-lined pipe. along with an unknown number of other utilities, which had all been buried two-to-three feet below ground for over 40 years. Two steel support pillars had been constructed on top of the utilities’ location at some point in the intervening years.
The only way to access this pipe full of utilities to figure out which one was leaking was to conduct utility potholing: exploratory excavation to find a buried utility. But this would be especially dangerous in this situation, given the types of utilities at play.
“[This utility tunnel] has liquid gas, fuel oil, cooled water, a little bit of everything,” explained GPRS Project Manager Stephen Layon. “They have a suspected leak because they took a thermal gun and saw the radiant heat coming out of the tunnel, and they also wanted to know, when they’re digging down, if there are any utilities popping out of this tunnel because they’ve used it to kind of hitchhike through the site without having to dig a really huge trench.”
Layon utilized a ground penetrating radar (GPR) scanner and electromagnetic (EM) locator to investigate the site of the suspected leak.
GPR scanners emit radio signals into the ground or a surface such as concrete, then detect the interactions between these signals and any buried or embedded objects like sewer pipes, electrical conduit, rebar, or post tension cable.
These interactions are displayed in a GPR readout as a series of hyperbolas that vary in size and shape depending on the type of material detected. GPRS Project Managers are specially trained to interpret this data to tell you what was located and provide you with an estimated depth for the object.
EM locators detect electromagnetic signals radiating from metallic pipes and cables. These signals can be created by the EM locator’s transmitter applying current to the pipe, from current flow in a live electrical cable, or from a conductive pipe acting as an antenna and re-radiating signals from stray electrical fields and communications transmissions.
Utilizing both his GPR unit and EM locator, Layon was able to locate the buried pipe full of utilities and pinpoint the location of the leak that the on-site personnel had detected with the thermal imaging gun.
“I located the tunnel, located the utilities around it,” he said. “Fortunately, the data was great. I could see down six-to-seven feet. I did see something that looked like a void… the data quality decreased from six-to-seven feet down to about one-to-two feet [in] the same area where the thermal camera indicated there was a leak…”
While utility potholing is a good method of locating utility lines during construction or repairs, it is time consuming, expensive, and not without risk – especially when you’re dealing with utilities such as gas or electrical conduit. The data Layon provided to the power generation plant mitigated the need for potholing, ensuring they only needed to dig once to find and repair the leaking utility line.
And Layon went above and beyond the original scope of work by also locating and mapping the expansion joints along the buried utility pipe.
In addition to marking out these findings on the ground with spray paint, Layon also logged all the data he collected into SiteMap® (patent pending), GPRS’ project & facility management application. With this tool, the facility’s staff will have 24/7, secure access to the data Layon collected on site, allowing them to not only plan a repair for the leak, but also any future O&M at or around the buried utilities.
Whether you need to locate utilities for an emergency repair or are looking to understand what’s underground before you begin a new construction project, GPRS Intelligently Visualizes The Built World® to keep you on time, on budget, and safe.
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Frequently Asked Questions
What does GPRS provide their clients who request utility locates?
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 a global positioning system (GPS) 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.
Does ground penetrating radar detect 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, including electromagnetic (EM) locating.
