Dive summary:

• Ground-penetrating radar, long used in some waste-site assessments, can generate two- or three-dimensional information about what lies beneath a planned construction site.
• Its use may be greatest at urban sites, where decades of uses might have left behind all manor of structures and voids that are invisible.
• The technology also offers opportunities for examining concrete slabs that are not accessible from both sides for X-ray analysis, is non-destructive for the materials being examined, and works on a variety media.

From the article:

We have been in the preconstruction phase of a brownfield project for about 18 months. In the process, we have been using a relatively new and still evolving set of technology tools, called ground penetrating radar (GPR).  ...