GPRS scans concrete two miles below the surface
SUMMARY: While the GPR technology we use has evolved since 2015, William Johnson’s harrowing story remains a testament to the work ethic of our field team.
Into the Depths of Data: a GPRS Project Manager’s Unconventional Journey Two Miles Below the Surface
“That was the darkest dark I’ve ever experienced. There was no sound, I had no idea where I was. Thank God the headlamp didn’t go out.” – William Johnson, Senior Project Manager, GPRS
Click the image above to watch the jobsite story video
In 2015, GPRS Senior Project Manager William Johnson found himself deeper underground than most professionals in his field will ever venture. Enveloped by the thick blackness of a Pennsylvania mine, Johnson stood alone, more than a mile beneath the surface. His only lifeline to visibility was the narrow beam cast by his helmet-mounted headlamp, which barely sliced through the subterranean void.
In the event of equipment failure, Johnson had been strictly instructed to remain stationary and await assistance. Curiosity compelled him to switch off the light briefly, to fully grasp the intensity of the darkness underground.
“That was the darkest dark I’ve ever experienced,” he remembers. “There was no sound, I had no idea where I was. Thank God the headlamp didn’t go out.”
Johnson’s assignment initially appeared routine, an ordinary call-out for a concrete scan. Having joined GPRS just months prior, Johnson anticipated a standard site visit.
“I had no real information about the job other than the fact that it was on a mining facility property, and they were interested in the slab thickness of a concrete pad that they had poured,” he explained.
Project Manager William Johnson used a SIR 3000 GPR controller back in 2015 when he was asked to scan a concrete pad more than two miles underground in a mine shaft in Pennsylvania. Today, he’d likely be using a Proceq scanner.
However, the parameters of the task shifted rapidly. After meeting his site contact, Johnson was directed to load his GPR equipment onto a waiting golf cart. Outfitted with the requisite protective gear, he descended with the crew into the shaft. Within 30 minutes, they had reached a location buried deep within the Earth’s crust, estimated to be between one and two-and-a-half miles below the surface.
Although other personnel were present at the site, they were occupied with their own duties and departed soon after arrival. Johnson was left to conduct the necessary scan in isolation. His mission was to assess the slab’s structural depth and integrity to determine whether it could bear the weight of a large industrial asset soon to be transported into the mine.
For this analysis, Johnson brought along what was then the industry benchmark: the SIR 3000 ground penetrating radar system paired with a 1600 MHz antenna. Weighing nine pounds, the unit offered robust imaging capabilities, but lacked the mobility and precision of contemporary platforms.
Technological advancements have since revolutionized this domain. Today, Johnson and his peers employ equipment such as the StructureScan Mini XT and the Proceq GPR Live: compact, fully integrated systems that significantly outperform their predecessors in accuracy, portability, and data resolution.
“With the new technology, depending on what unit you have, it’s either all wireless or an all-in-one unit,” Johnson said. “The unit I currently use is the Mini XT, and with that you can attach a walking stick to it and that houses the GPR unit as well as the computer system. It’s all-in-one; no wires, no dolly, it’s significantly lighter, it’s way more accurate, and the quality of the data is a lot better as well.”
This progression in GPR instrumentation reflects broader developments within the mining industry, a sector that remains a cornerstone of U.S. industrial output. In 2021 alone, the mining industry (excluding oil and gas) contributed $61.24 billion to the national economy, more than double the $29 billion added in 1998. Approximately 13,000 mines remain operational across the country.
Despite its long history and economic importance, mining continues to be categorized as high-risk. Nevertheless, safety records show consistent improvement. In 2020, the Mine Safety and Health Administration (MSHA) reported 29 mining-related fatalities, marking the sixth year in a row that the number remained below 30. Of those, just five occurred in coal operations, a historic low that underlines the impact of enhanced safety measures and operational protocols.
Still, the margin for error in such an environment is razor-thin. Proper planning and accurate data acquisition are essential not only for operational success but for the safeguarding of human life.
Even with the legacy limitations of the SIR 3000, Johnson was able to complete the scan and derive the critical measurements required. Whether it took two or four hours remains a mystery – disorientation is an expected consequence when working miles underground – but the outcome was what mattered. His accurate assessment enabled the client to proceed confidently, knowing exactly where equipment placement was safe and structurally viable.
“It went very well,” Johnson noted. “The concrete thickness was thankfully very easy to ascertain, and they also wanted me to mark any significant changes within the concrete thickness every several feet. So, I just took spray paint and made those markings.”
Reflecting on that day, Johnson acknowledges the experience left an indelible mark on his professional journey. He’s encountered numerous unusual situations on the job, but the subterranean mission remains singular in both its challenge and intrigue.
“I’ve had different work phones throughout the years, but the photos I took from this job are ones that I make sure to transfer to my new phone every time,” he said. “I actually have them saved on my personal phone too, because family members are always asking what I do for a living. This is a very good conversation starter.”
Johnson’s story exemplifies the extraordinary range of environments in which GPRS operates. More than that, it underscores the company’s commitment to technical precision, adaptability, and client safety across even the most extreme project conditions. His narrative affirms GPRS’ mission to help clients Intelligently Visualize The Built World™, no matter how far beneath it that world extends.
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