What a utility quality level actually promises

October 12, 2026 · 4 min read

That distinction gets lost constantly. A letter that sounds like a school grade invites the reading that QL-A is the careful job and QL-D is the cheap one. It is not a scale of care. ASCE 38-22 is a standard for recording provenance: each level tells you what method produced a given utility's position, and therefore how much weight that position can carry when you set a pile, cut a trench or sign a drawing.

QL-D: what the records say

QL-D is information from existing records and oral recollection. As-builts, utility atlases, one-call sketches, and the foreman who remembers where the gas line went in.

It is genuinely useful. It tells you which utilities are probably present and roughly where to start looking, which is what you need at the planning stage. What it cannot tell you is position. As-builts record design intent, not what the crew did on the day, and a line shown dead straight on a drawing may have been bent around a boulder nobody wrote down. QL-D is where to look, not where it is.

QL-C: what you can see from the surface

QL-C surveys the utility features you can see standing on the ground — manhole rims, valve boxes, meter pits, pedestals, pole risers — and correlates them with the QL-D records.

The surveyed points are real, and that is what makes QL-C deceptive. The coordinates on the drawing carry survey accuracy, so the drawing looks authoritative. But the line drawn between two surveyed manholes is still an assumption that the pipe runs straight between them at constant grade. The endpoints are measured; the alignment between them is inferred. On a utility that was laid around an obstruction, that inference can be several feet off while the drawing looks precise to the hundredth.

QL-B: what geophysics can find

QL-B is designating: locating the utility from the surface with geophysical methods — electromagnetic induction, ground-penetrating radar, magnetics — marking it on the ground, and surveying the marks.

This is the level that does the most work on most projects, because it is the first one that measures the utility itself rather than something attached to it. It gives you horizontal position along the whole run, including the bends nobody recorded.

Two honest limits. First, depth from surface geophysics is an estimate, not a measurement — it depends on soil properties and the method, and it should be labelled as approximate wherever it appears. Second, QL-B finds what the method can detect: an unmarked clay tile, a plastic water service with no tracer wire, or a line under reinforced concrete may simply not respond. Nothing found is not the same as nothing there.

QL-A: what someone actually saw

QL-A means the utility was exposed — normally by vacuum excavation — and its position surveyed at the point of exposure. Horizontal and vertical, plus size, material and condition.

This is the only level where a human being laid eyes on the pipe. It is also the only level that gives you a depth you can design against rather than allow for.

It is used selectively for the obvious reason: every QL-A point is a hole. The usual pattern is QL-B across the site to establish what is there and where it runs, then QL-A test holes at the points where being wrong is expensive — crossings, tie-ins, pile locations, the spot where the new storm line has to thread between two existing mains. A QL-A point is bought to retire a specific risk, not to raise the grade of the drawing.

Quality level is a property of the utility, not the survey

Here is the part that causes the most trouble in scopes and contracts. The quality level attaches to each utility segment on the drawing, not to the project as a whole.

"We had a QL-B survey done" is not a meaningful statement about a site. A properly depicted drawing carries a quality level per segment, and a real site produces a mix: the gas main designated to QL-B and test-holed to QL-A at the crossing, the electric duct bank at QL-B, an abandoned line at QL-D because the records mention it and nothing was detected, a telecom service at QL-C off two surveyed pedestals.

That mix is not a sign of an incomplete job. It is the deliverable. A drawing that claims one uniform level across every utility on a site is either telling you less than it knows or more than it found out.

What to put in a scope

Three things make a subsurface utility scope work, and none of them is a letter on its own.

1. Name the decisions the data has to support. Pile locations, a trench alignment, a tie-in elevation. The decisions determine where you need QL-A and where QL-B will do.
2. Ask for the quality level depicted per utility segment, with the method noted. That is what ASCE 38-22 asks for, and it is what tells a reviewer which lines to trust.
3. Say how depth is to be reported — measured at QL-A test holes, estimated elsewhere, and labelled as such on the drawing.

If a proposal quotes you a single quality level for an entire site, that is worth a question before it is worth a signature.

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