The Joint at Slabtown

Joint at Slabtown, 3D Data over PhotoJoint at Slabtown, 3D Data over Photo

Our wide range of expertise and available services differentiate us from other GPR providers.  This recent project in Portland, OR demonstrates our ability to adapt to unexpected challenges, overcome them quickly, and keep your project moving forward on schedule and within budget.

“When your only tool is a hammer, every job looks like a nail.”

2D vs 3D GPR Services

In the world of ground penetrating radar services, there are two primary methods of doing work: realtime 2D locating (find it, mark it, go home) and 3D mapping (collect data, process data, deliver findings).  We discuss these methods in more detail on a few of our previous articles.  The gist of it is this: realtime 2D locating is the quickest method for small scale and low complexity areas; 3D mapping is usually the most cost effective method for large scale and high complexity areas.  Concrete GPR has the expertise to seamlessly integrate both methods, giving us the range of tools to finish your job as quickly and inexpensively as possible.

The original concrete imaging scope for The Joint at Slabtown was to scan the ceiling for post-tension cables prior to installation of anchors for new MEP installation.  The space was an empty shell, and this was the first TI after initial construction.  In this small space, it was most efficient to bring us in before the congestion from other trades, and we rapidly marked the location of all PT cables at their low point in the slab, when the depth and concrete cover were unsafe for anchor installation.  This allowed the MEP trades to come in later and install their hangers / seismic anchors with a high degree of freedom.

Joint at Slabtown, 3D GPR Data
Joint at Slabtown, 3D GPR Data

Electrical Conduit Conflicts

At the outset, nobody was concerned about the floor slab because it isn’t post-tensioned.  As part of our service, we quickly inspected a few areas of the floor to verify the as-built conditions.  Although we confirmed that the slab is not post-tensioned, we also found electrical conduits.  A lot of electrical conduits.  The lower level was a parking garage with insulation tacked to the ceiling, and the site information indicated that electrical was surface mounted to the underside of the slab.  It isn’t — it’s all inside the slab, and if the cores had been drilled blind as intended, several live conduits would have been cut.

Rapid and Accurate 3D GPR Scanning

We quickly scanned all of the floor hole locations and identified safe drilling positions for each…except one.  One area was so congested with rebar and conduit that 2D locating was not sufficient to accurately identify a safe location to drill.  Instead of burning time — and money — attempting to brute force the hole with inadequate realtime scanning, we collected a small 3D grid, broke out the laptop, and processed the data on-site.  With the 3D GPR data grid, we were able to confidently map all conduit and rebar, and provide a safe location to drill.

All scanning services were provided before lunch.  All holes were safely drilled before end of day.