Quality Level B (QL-B)

The ASCE 38 level for utilities found by field geophysics — electromagnetic locating and ground penetrating radar — and surveyed. QL-B gives a reliable horizontal position and an estimated depth.

QL-B is where most locating work lands, and understanding its limits is the difference between using the data well and over-trusting it. The horizontal trace is generally sound on a well-coupled line; the depth is an interpretation that degrades with bleedover, parallel runs, and soil conditions. QL-B tells a designer that something is there and roughly where it runs, which is enough to plan around and not enough to build to.