Post Tension Cable Locating
at Brownie Septic Inc. in Orlando, Florida

GPRS was contacted by Brownie Septic Inc. of Orlando, FL to mobilize to a project on Sand Lake Road in Orlando, FL. Brownie Septic had been asked to route a new storm/drain line from the roof of a shopping plaza (The Dellagio Plaza) thru the post tension concrete slab and tie into the main storm system in the ground below. There was only one location that Brownie Septic needed to drill but they knew that they could not take the risk and hit a post tension cable in the concrete.  Knowing that ground penetrating radar was one of the best, most efficient, and non-destructive ways to locating post tension cables in concrete they contact Ground Penetrating Radar Systems, Inc. of Orlando, FL. Chris Moore with GPRS priced the project competitively and mobilized to the site within 2 days to meet Brownie Septic’s schedule.

Originally it was determined that GPRS would attempt the survey from the top of the concrete.  Brownie Septic had informed GPRS that the slab would be roughly 14” thick. The antenna which GPRS utilizes is typically good for 18-20” of concrete depending on the amount of reinforcing steel present. The survey was conducted from the top of the concrete and it was apparent to GPRS that the concrete would need to be surveyed from the bottom as well. Surveying the slab from both the top and bottom would all but ensure that Brownie would not hit any post tension cables. 

The survey revealed several post tension cables running directly thru the area where Brownie Septic had proposed to drill. The core would have gone thru a section of Banded Post Tension Cables thus damaging multiple cables at once.  In the picture below you will notice the post tension cable markings mapped by GPRS. You will also notice the orange flag where Brownie had piloted a small hole. You can then see the outline of where Brownie had hoped to drill their hole. Notice how close the hole layout is to several post tension cables around.

The ground penetrating radar survey revealed that the original layout of the drilling location would have to be altered. The alteration was enough that Brownie needed to go back to the planning/designing team and ask them how to proceed. In this case ground penetrating radar not only saved the building from structural damage and the cost of repair but saved Brownie Septic from having to drill multiple locations at their own cost. They could “re-plan” the job and move forward. 

All in all Brownie Septic was pleased with the results of the survey. For the last 10 years Ground Penetrating Radar Systems has specialized in locating post tension cables (as well as other types of reinforcing steel) in concrete prior to core drilling and saw cutting. 

If you would like more information contact your local ground penetrating radar representative.