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To Drill or Not To Drill?

To Drill or Not To Drill?

CSDA GPR Contractor Helps to Revise Plumbing in New Charlotte Construction

Charlotte, NC is one of the largest and fastest growing cities in the Southeast U.S, only surpassed by Jacksonville, FL. There is currently more than $1.7 billion of construction projects underway. Of that, 948,000 square feet of retail space and 8,500 residential units are under construction or in the planning stages.

In June, Penhall Company was asked to scan the slab of a multi-use building under construction, which would eventually house retail shops and luxury apartments. The scans were intended to learn more about the structure of the building, identify the locations of post tension cables and make sure the areas indicated for plumbing holes were clear of obstacles. Penhall used a GSSI Mini HR and GSSI Palm with SIR-4000 for the GPR scanning. X-ray could have been used in this case, but GPR is much faster and safer, and workers wouldn’t be exposed to radiation that comes with using X-Ray. After the scans were complete, Penhall would drill the holes for general plumbing.

Good thing the general contractor, Bliss Contracting, asked them to scan the slab before cutting! Penhall discovered that the original plans asked for the plumbing holes to be cut directly over slab bands and post tension cables. Also, the eight-foot wide mechanical closet was situated directly over an eight-foot slab band, so any penetrations into that room would have to go through the slab band, which was not ideal.

Turns out, the design architect did not consult the structural drawings when designing the plumbing layout. To complicate matters, there was an overabundance of structural reinforcement in some areas, such as slab bands, thicker concrete and columns.

Penhall Company walked the general contractor through their site markings. Cutting into five of the six holes would be extremely problematic, as the markings identified hazards such as post tension cables. Based on the scan site markings, Penhall advised the contractor to stay clear of the marked hazards, which ultimately led to new plumbing plans.

When the new plumbing plans were complete, Penhall again scanned the slabs to confirm that the new locations were clear.

Once the locations were cleared for cutting, Penhall drilled six three- to six-inch diameter holes in the concrete eight- to ten-inches thick with a Hilti core drill. The cutting went without incident – nice clean holes.

Safety is always the number one concern on any jobsite. GPR scanning is imperative when drilling through concrete to identify obstacles and ensure the safety of workers. While the discovery of the problematic drilling areas set the project back about two weeks, it ultimately saved the project money, as the holes were cut right the first time (upon redesign) and without incident.

When asked why they were selected for this job, Penhall Sales & Marketing Manager Stella Pudewell stated, “Penhall Company knows concrete. Having a division that specializes in concrete scanning is immensely complimentary (if not necessary!) when cutting will follow. Our Regional Field Supervisors, like Patrick Baldwin, have years of experience, which allows our clients to have peace of mind that their project will be completed successfully.”

CSDA GPR contractors are playing an increasingly important role in the modification and renovation of new and existing concrete structures. Employing a CSDA contractor ensures that any cuts made or holes drilled can be done without hitting any implements, thus keeping the safety of all operators on the jobsite a priority. Additionally, the structural integrity of the building remains intact.

The article published in the printed Concrete Openings September issue has since been corrected. Penhall Company does not make recommendations on redesign, nor where to cut. Only recommendations are made to stay clear of marked hazards based on findings.

Company Profile

Penhall Company has been the go-to concrete services partner for a wide-range of industries since 1957. What began as a single flat saw operation has developed into an expansive offering of concrete solutions, including concrete scanning, cutting, sawing and breaking/removal. They have specialized in concrete scanning for more than 20 years. Penhall employs expertly trained analysts that use state-of-the-art GPR equipment to find common embedded objects and other subsurface hazards that are hidden in the concrete. Penhall Company has been a member of CSDA since 1999.


General Contractor

Bliss Contracting

CSDA Cutting Contractor

Penhall Company

Stella Pudewell

Tel: 707-363-9822


Methods Used

GPR, Core Drilling

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