SUE Quality Levels Explained: QL-D, QL-C, QL-B, and QL-A
A line on a drawing tells you nothing about how it got there. Quality levels are the standard that fixes that.
The Problem Quality Levels Solve
On an unlabelled drawing, a utility traced in the field and a utility copied off a 1970s as-built look identical. They carry wildly different confidence, and a designer has no way to tell them apart. ASCE 38 fixes that by requiring each segment to state how its position was determined.
The current edition is ASCE 38-22. Its companion, ASCE 75, covers recording new installations as-built.
QL-D — Records and Recollection
Information from existing records, utility owner drawings, and what people remember. No field verification of any kind. It is the cheapest step and every project starts here, because records research narrows where the field crews look.
The failure modes are well known: field routing changed during construction, repairs rerouted segments, additions were made by whoever was on site, and some records were never created. Treat QL-D as a hypothesis.
QL-C — Surveyed Surface Features
Visible surface evidence — manholes, valve boxes, meters, pedestals, vault lids — surveyed and correlated with the records. Better than QL-D because someone walked the site and measured what can actually be seen, and it often turns up utilities the records omit entirely.
What it still does not do is trace the buried run between the surface features. The line between two manholes is inferred, and buried runs are not always straight.
QL-B — Field Designation
Utilities detected with field geophysics — electromagnetic locating and ground penetrating radar — and surveyed. This is where most locating work lands and where most of a corridor should sit.
QL-B gives a reliable horizontal position on a well-coupled line and an estimated depth. The estimate is the part people over-trust: it degrades with bleedover, with parallel runs, and with soil conditions. QL-B tells you something is there and roughly where it runs. It does not tell you what to build to.
QL-A — Physically Verified
The utility has been exposed, normally with a vacuum test hole, and its position, depth, material, and outside diameter measured and surveyed directly. QL-A is the only level that reports a measured depth, and the only one that reports material and diameter at all, because no surface method can determine them.
It is also the most expensive per point, which is why it is placed rather than blanketed.
How to Scope Without Overbuying
Normal practice is QL-B designation across the whole corridor to establish what is there and where it runs, then QL-A test holes only at the points where the design actually conflicts: crossings, proposed foundations and piers, and bore entry and exit. A firm that proposes QL-A on every utility across a corridor is usually overselling, and it inflates the scope without improving the design.
Tell the firm what stage the design is at and what decisions the data has to support. Scope follows from that, and so does the quote.
Frequently asked questions
Is SUE the same as private utility locating?
The instruments overlap; the deliverable does not. A private locate puts marks on the ground so a crew can dig safely, usually within days, with no surveyed record afterwards. SUE runs the same field geophysics but ties every mark to project survey control, adds records research and test-hole verification, and produces a signed and sealed drawing where each segment carries its own quality level. If you are digging soon, you want a locate. If you are designing, you want SUE.
Do we need QL-A on every utility?
Almost never. Designate the corridor at QL-B, then place QL-A test holes where a conflict actually exists. Every test hole is a separate mobilization of separate equipment, and blanket QL-A spends that money on utilities the design never comes near.
Can a quality level be assigned after the fact?
Not credibly. The level describes how the data was collected, so it has to be recorded by whoever collected it. A drawing that assigns quality levels retroactively to data of unknown provenance is asserting confidence it cannot support, and that is exactly the situation the standard exists to prevent.
Does a SUE drawing replace calling 811?
No. A SUE deliverable is a design document, not a locate ticket, and it does not reflect anything installed, repaired, or abandoned since the survey date. File the one-call ticket before every excavation regardless of what the design package says.
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