GPRS deployed our precision concrete scanning services to help solve a mystery at a nearly 200-year-old church.
GPRS Project Manager Andrew Machemer was called out to Christ Episcopal Church in Downtown Reading, Pennsylvania, to examine a curious looking stone block that crews noticed when they were beginning renovations on the building’s exterior.
Christ Episcopal Church was founded in 1762 and is the oldest English-speaking congregation in Reading. The present building was built between 1825-1826 and designed by American architect Edward Tuckerman Potter, whose claims to fame include the Mark Twain House in Hartford, Connecticut, and Nott Memorial Hall at Union College.
The church today features many Neo-gothic elements which were added during a major renovation in 1847. In 2020, the church was awarded a grant from the Pennsylvania State Historic Preservation Office to stabilize and protect the masonry of the buttress walls supporting its steeple and historic façade.
When these ongoing restoration efforts uncovered the strange stone, church historians dug into the archives looking for an explanation.
“I believe they found a newspaper article from the Reading Eagle from the 1820s,” Machemer explained. “They found an old mention of a ten-inch by six-inch copper time capsule at this exact spot, but nobody at the church currently had any knowledge about it. So, they wanted to scan the block and see if anything was there.”
While GPRS’ concrete scanning and imaging services aren’t regularly utilized for historical investigation, this isn’t the first time we’ve been asked to look for a time capsule embedded within the walls of a historic Pennsylvania church.
Machemer deployed multiple tools to examine the block and surrounding masonry, including a metal detector and an electromagnetic (EM) locator.
But it was the concrete scanning GPR antenna that produced the most promising data.
“[We found] what clearly looks like what we think would be indicative of a metallic object fitting the description of what they had thought existed,” Machemer said. “So, the data looks very promising of an object being inside that concrete slab.”
The church was thrilled by what Machemer discovered.
The Reading Eagle – the same newspaper in which church historians uncovered the initial evidence of the time capsule – covered Machemer’s findings in an article which you can read here. And the church is now planning on excavating the object and – if it really is a time capsule – opening it during their bicentennial celebration in 2026.
Explaining GPRS’ Industry-Leading Concrete Scanning Services
Assisting with historical preservation isn’t the primary way GPRS utilizes our precision concrete scanning services; we’re usually helping contractors, facility managers, architects, and engineers stay on time, on budget, and safe.
GPRS Project Managers utilize GPR scanners to identify materials or voids within concrete slabs. This technology enables precise detection of hidden objects and their exact locations.
GPR is a non-destructive detection and imaging method in which a radio signal is sent into a concrete structure. The radio wave bounces off any material it encounters and creates a reading that displays these “bounces” as hyperbolas. An experienced GPR technician interprets this reading to determine the type of material located.
Scanning concrete with GPR reveals rebar, post tension cables, electrical conduit, voids, and more. This is also an effective method of structural review including concrete slab measurement and rebar spacing.
Concrete should be scanned before any excavation or renovation work begins. This includes coring, drilling, cutting, and any other activities that could compromise the concrete’s strength.
With over 500 SIM-certified Project Managers strategically stationed across the United States, GPRS is a professional concrete scanning company you can rely on to be there when you need us, and to provide you with the accurate data you need to protect your people, your schedule, and your budget.
Our industry-leading accuracy can be attributed to your adherence to the Subsurface Investigation Methodology (SIM).
SIM is the underpinning of our training program, and the concrete scanning and utility locating processes our Project Managers use daily. It’s the first comprehensive specification for professional utility locators and concrete scanning technicians. It aims to raise the quality of subsurface investigations by combining the requirements of experienced-based training, tested technologies, and proven application methods to create an industry standard.
All GPRS Project Managers are required to achieve SIM certification, a process that involves completing a minimum of 320 hours of field training and 80 hours of classroom training. SIM also requires that all utility locates and concrete scans involve the use of multiple technologies, ensuring that the results are repeatable and accurate.
GPRS is so confident in the accuracy of our SIM-certified concrete scans that we introduced the Green Box Guarantee, which states that when we place a Green Box within a layout prior to you anchoring or coring that concrete we guarantee that the area within the box will be free of obstructions.
If we’re wrong, we pay the material cost of the damage.
From unearthing time capsules to protecting the integrity of your concrete slabs, GPRS Intelligently Visualizes The Built World® to keep your projects on time, on budget, and safe.
What can we help you visualize?
Frequently Asked Questions
Can GPR determine the difference between rebar and electrical conduit?
Ground penetrating radar (GPR) can accurately differentiate between rebar and electrical conduit in most cases. We have an extremely high success rate in identifying electrical lines in supported slabs or slabs-on-grade before saw cutting or core drilling.
Additionally, GPRS can use EM locators to determine the location of conduits in the concrete. If we can transmit a signal onto the metal conduit, we can locate it with pinpoint accuracy. We can also find the conduit passively if a live electrical current runs through it.
The combined use of GPR and EM induction allows us to provide one of the most comprehensive and accurate conduits locating services available.
How is GPR used to identify tendons vs. rebar in a post-tensioned slab?
In post-tensioned structures, we typically find one mat of support rebar near the base of the slab. This mat is generally consistently spaced and remains at a constant elevation. Post-tension cables are generally found above this support mat and “draped” throughout the rest of the structure. The elevation of the cable is usually high near the beams and column lines and drapes lower through the span between beams and column lines. Knowledge of these structural differences allows us to accurately differentiate between components. Our Project Managers will leave you feeling confident in our findings and in your ability to drill or cut without issue.
