It's a very common practice for environmental consultants to get soil samples around underground storage tanks (USTs). The selection of drilling locations depends on a lot of factors and sometimes it's preferable that they are located as close as possible to USTs without risking damaging them. Ground penetrating radar (GPR) is a great tool to use to delineate UST scopes due to its very high lateral resolutions.
GPR can be used to delineate scopes of USTs made of steel or fiberglass. Even if a concrete slab is constructed on the ground surface for the protection of UST, it's a safe practice to conduct a GPR survey to make sure the UST does not extend beyond the scope of the concrete slab. We have found in occasions a fiberglass tank can extend beyond its concrete slab on the ground surface with its dome-shaped ends, sometimes due to later pavement constructions. Pictures below show GPR signal differences between a fiberglass UST and a steel UST.