Home › Geophysical services › Utility locating and subsurface utility engineering
Applications
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.
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 — from existing records. As good as the records, which on older sites means it may be wrong.
- QL-C — records correlated with visible surface features: manholes, valve covers, meters, poles.
- QL-B — designated by geophysics. Horizontal position established by surface instruments and surveyed. This is the level most projects actually need, and it is the core of what we do.
- QL-A — the pipe has been seen and measured, through a test hole. Vertical and horizontal position to survey accuracy.
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.
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.
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.