For soil and water samplings in environmental investigations, drilling locations are usually chosen strategically, as unlimited locations are not an option. One type of location of interest is where former underground storage tanks (USTs) were, but have now been removed.
Drilling locations are preferably chosen in and around excavation areas of former USTs to determine the levels of possible contamination. A few feet of difference could mean catching or missing contamination.
However, sometimes exact excavation locations are not known due to lack or inaccuracy of records. Actual excavation areas could be paved over many times and no visible signs of excavation are left.
Ground penetrating radar (GPR) is a great tool not only for locating USTs themselves, but also their excavation areas.
Below are some GPR profiles showing very good evidences of past excavations:
As any other geophysical tools, GPR is not 100 percent fail-proof. Some past excavation areas could be much less obvious in GPR data.
Below are a couple of GPR data examples where excavation areas are kind of shown, but not very convincing.