Utility locating and subsurface utility engineering

One-call marks the utilities their members own. Everything else on the site — the private network, the abandoned lines, the ones nobody has a record of — is the part that stops a job.

A towed ground-penetrating radar cart behind a survey vehicle in a closed lane on a downtown city street, with traffic barrels and high-rise buildings on either side. — Designating in a closed lane downtown. The survey runs in the window the lane closure allows, which is usually the constraint that sets the method.

Quality levels are not grades of effort

ASCE 38-22 defines four quality levels, and they describe where the information came from, not how hard anyone tried. QL-D is the records; QL-C is the records correlated with what can be seen at the surface; QL-B is horizontal position established by geophysics; QL-A is the pipe physically exposed and measured. What each one actually promises, and the one confusion that costs money, is set out in our note on utility quality levels.

QL-B designating is the core of what we do, and it is the level most projects actually need. Only QL-A involves anyone seeing the utility. We do not excavate, so we designate to QL-B and coordinate with a vacuum excavation contractor where QL-A is required — and we will tell you where it is required rather than letting a QL-B drawing be used as though it were QL-A.

Paint marks on an asphalt parking lot showing a located service running across the pavement, annotated with depth and size, with a ground-penetrating radar cart standing on the line. — QL-B on the ground. The line is where the instrument put it, annotated with size and depth, and surveyed before the paint weathers off.

Two methods, because one is not enough

Electromagnetic locating — direct connect where a line can be accessed, induction where it cannot — is the primary tool for anything conductive and traceable. It gives the best position and the most reliable identification.

Radar covers what EM cannot trace: PVC and concrete pipe, ducts, abandoned lines with no continuity, and the trench backfill that often betrays a service whose contents are invisible. Running both is standard on our SUE work, because the utility most likely to cause an incident is the one nobody could trace.

A commercial parking lot with an extensive network of red paint marks across the pavement recording located services, a radar cart at the edge of the marked area. — A private network on a commercial site, marked across the area of works. None of this is on a one-call ticket, because no member utility owns any of it.

What limits it

Reinforced concrete, dense congestion, deep services and heavy wet clay all degrade coverage. A non-conductive pipe in a trench that has fully consolidated may leave no detectable signature at all.

That is why the deliverable states confidence per feature rather than drawing everything with the same line weight. A plan on which a traced live main and an inferred anomaly look identical is actively dangerous, and it is how excavation crews end up with more confidence than the data ever supported.

Equipment and capability

ASCE 38-22 QL-D through QL-B
Direct connect and inductive EM locating
GPR for non-conductive and abandoned lines
APWA color-coded surface marking
Survey-grade positioning of every designated line
Attributed CAD and GIS deliverables

What you receive

APWA-coded marks on the ground, and a drawing in which every line carries its quality level, its method of detection and its depth confidence — so the designer can see which parts of the picture will carry weight and which will not.

Ask before you commission

Tell us the target, the ground and the constraint and we will say whether this method answers it, whether it needs a second method alongside, or whether something else entirely is the better route. That conversation is free and it is usually short.

(844) 300-6GPR sales@geosearches.com

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