EM Line Locating · Pre-dig · dual-method
+ GPR Utility Clearance Survey by EM.
The complete pre-dig clearance: passive sweep, active EM tracing of every conductive line, GPR imaging for non-conductive lines and confirmation, sonde tracing for drains, and depths at the dig point. The single survey that makes breaking ground safe — and the everyday private locate done right.
Free phone consult · No pressure · Mon–Sat 8am–6pm PT
Best suited for
Why it's used
- One survey covers conductive AND non-conductive lines
- Dual-method is the standard of a defensible locate
- Depths and a marked dig box at the work area
- The combined offering this whole discipline exists to deliver
How it works
- 1
Passive sweep first
The survey opens with a power-and-radio passive sweep — flagging energised cables and conductive lines before anything is connected or dug. Safety-critical lines surface first.
- 2
Active EM tracing
Every known and discoverable conductive utility is traced precisely by direct connection, clamp, or induction — water, gas, electrical, telecom, tracer-wired plastic — each marked with depth at the dig point.
- 3
GPR imaging
GPR sweeps the area for what EM can't see: non-conductive plastic and clay lines, concrete ducts, unknown anomalies, and confirmation of the EM traces. The two methods close each other's gaps.
- 4
Mark, depth, document
The dig box is marked, depths noted at crossings and the work area, drains sonde-traced where present, and the clearance documented. Where digging follows, hand-exposure or vacuum potholing verifies the critical lines before machinery.
Frequently asked
What is a private utility locate and why isn't BC One Call enough?
BC One Call (the provincial one-call service) notifies member utilities to mark their PUBLIC lines up to the property line — it does not cover the privately-owned lines beyond it: your water service, irrigation, private power to a garage, gas to a fire pit, septic, and so on. A private utility clearance survey finds those. Every responsible dig uses both: call BC One Call for the public locates, and hire a private locate for everything on your side of the line.
Why does a proper clearance need both EM and GPR?
Because no single method finds everything. EM traces conductive lines precisely but is blind to non-conductive plastic and clay; GPR images the subsurface including non-conductive lines but can't label which conductive line is which the way an EM trace can. Run together, EM identifies and traces the metal and tracer-wired lines while GPR catches the plastic, the clay, and the unknowns — and each confirms the other. Dual-method is the standard a defensible locate is held to.
Does a clearance survey guarantee nothing will be struck?
No honest locator promises that — abandoned lines, unmarked private installs, and the limits of every instrument in difficult soil all exist. What a proper dual-method survey does is reduce the risk as far as detection technology allows, and the responsible final step before machinery is hand-exposure or vacuum potholing at the critical crossings to lay eyes on the line. We locate thoroughly and we're candid that potholing is the last word on safety.
How soon before digging should the survey happen?
Close enough that the marks are still fresh and the site hasn't changed — typically within a few days of the dig, and re-checked if work is delayed or the ground is disturbed in between. For pros, scheduling the clearance into the job sequence (after BC One Call, before excavation) is the pattern that keeps crews moving without gambling on stale marks. Notice-driven and pre-scheduled clearances both get prompt booking.
Related EM methods
Active EM Line Locating
Apply a known frequency to a target line and trace only that line — the precise, unambiguous core of electromagnetic locating. Direct connection or signal clamp puts a traceable signal on a specific conductive utility so it stands out from everything else in the ground.
ViewPassive EM Sweep Locating
Sweep an area for the signals buried metal already carries — live power at 50/60 Hz and re-radiated radio energy — to catch energised and conductive lines before a dig, without connecting to anything. The fast first pass that makes sure nothing live gets missed.
ViewSonde Drain & Duct Tracing
Push a sonde — a small battery transmitter — through a non-metallic pipe, drain, or duct, and trace it from the surface as if it were a metal line. The EM answer for plastic, clay, and concrete lines that carry no signal of their own.
ViewDepth Estimation & Utility Mapping
Add the third dimension and a permanent record: estimated burial depth at every point of interest, and a marked, measured map of what's underground — the deliverable that turns a one-day locate into a lasting site asset.
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EM + GPR Utility Clearance Survey across BC
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Locate before you dig. Both methods. One crew.
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