Underground Infrastructure - June 2023 - 32

Asset Management
GPR barely resembles the equipment GPRS project managers
used when the company was founded in 2001. And that equipment
is lightyears ahead of the GPR units of even a decade prior.
Yet, while this ever-evolving technology reigns supreme as
the premier choice for utility locating and concrete scanning,
its origins are far removed from the construction industry that
relies on it so heavily today.
Decades of development
GPR technology is older than one might expect.
Dr. Andrew Kozlowski of the New York State Museum tracGPRS'
John Kessinger pushes a ground penetrating radar scanner across
a snowy yard to locate buried utilities. GPR technology has advanced in
leaps and bounds since Kessinger, now GPRS' contract Locating manager,
was last in the field. (Photo courtesy of GPRSl)
fies subsurface elements, either underground or within a surface,
such as concrete. GPR can detect both metallic and non-metallic
objects, meaning that it can find all types of buried utilities.
GPR works by sending a radio signal into a structure or underground
and reading the " bounce " of that radio wave off any
material it encounters. These bounces are displayed as hyperbolas
on the GPR's display. An experienced technician can then
interpret this reading to determine the type of material located
and its precise location.
The ability to accurately map underground or encased infrastructure
allows construction and excavation professionals
to plan groundbreaking and other destructive activities more
efficiently. By knowing where not to dig, cut or core, these professionals
eliminate the risks associated with striking buried
utilities or severing structural components, such as rebar or
post-tension cables.
It's not uncommon for GPRS to be called to a site to conduct
a single area locate or concrete scan, only for the scope of
the project to expand as the contractor realizes the potential of
the company's services.
Merrell and the GPRS team have conducted hundreds of
these scans at the Ford site, investigating both below the earth
and within concrete structures. Over the time on the project,
GPR technology has seen improvements that allow Merrell and
his team members to provide a clearer image of the property's infrastructure
today than they could have even just a few years ago.
The UtilityScan unit Merrell has used much of the time
on the Ford campus is being phased out of GPRS' arsenal in
favor of the ImpulseRadar PinPointR GPR Scanner. With its
dual-channel operation and internal global positioning system
(GPS), the PinPointR can accurately locate items both shallow
and deep in the earth in a single pass over the surface. This improves
locating efficiency and decision making.
" I think the ImpulseRadar is the next big thing, " Merrell said.
" It uses multiple frequencies simultaneously. It has good resolution
deep, but then you can toggle over, and you can get great
resolution shallow. It's just an incredible piece of equipment. "
Whether it's the UtilityScan or the ImpulseRadar, modern
32 JUNE 2023 | UndergroundInfrastructure.com
es its origins back to the early 1930s, when it was developed to
measure the thickness of glaciers.
It would be another 30 years, however, before the technology's
capabilities were explored in earnest.
" The hardware and software made tremendous technological
advances in the 1960s, 1970s and finally became affordable
in the mid-1980s, " Dr. Kozlowski wrote.
In 1972, a GPR unit called ALSE (Apollo Lunar Sounder
Experiment) was carried by the Apollo 17 capsule as it orbited
the moon. ALSE operated on three radio wavelengths - 5, 15
and 150 Mhz - and radar data of the moon was recorded on
70-millimeter photographic film. The data ALSE collected provided
profiles of the lunar surface and subsurface.
As with any technology, GPR's capabilities only expanded
once the equipment became widely available. Still, at the dawn
of the new millennium, the construction and excavation industries
had yet to truly realize its potential for eliminating subsurface
damage.
At this point, underground utilities were primarily located
based on the as-built drawings created when the lines were
installed. As any construction professional will tell you, those
drawings should really be called " as-intended " because they are
rarely an accurate representation of what's underground.
For scanning concrete, the only option that existed prior to
GPR was X-Ray. This was a costly, time-consuming and dangerous
tool, as all or most of a site needed to be cleared to protect
workers from accidental irradiation during a scan.
GPRS President and CEO, Matt Aston, is considered a pioneer
in bringing GPR to the construction industry. It started
in 2001 when he happened upon an advertisement for GPR
rental while flipping through a magazine. He was well-versed
in the risks associated with cutting or coring concrete - his
father owned a concrete company - and had seen utility lines
and other subsurface objects accidentally damaged during construction
projects.
Aston seized the opportunity to bring GPR technology to
the construction industry. And GPRS was born.
Concrete scanning was GPRS' first service line, and GPR
was the primary tool used for the task. Unlike X-Ray scanning,
GPR requires access to only one side of a slab or structure. Also,
unlike X-Ray, GPR emits no harmful radiation and requires no
prior set-up.
GPR's final advantage over X-Ray? It keeps evolving.
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