Underground Utility Scanning for Private Utility Lines
Many property owners and contractors assume that a free call to the local one-call center before digging takes care of every buried line on a site. It does not. One-call services, such as 811 in the United States, notify the utility companies that are members of the system, and those companies mark the lines they own. On most sites, that ownership stops at the meter or the property line. Everything beyond that point is private, and nobody is obliged to mark it for you.
That gap is where a surprising number of utility strikes happen. This guide explains what counts as a private utility, why these lines are so often missed, and how professional scanning closes the gap.
What Counts as a Private Utility?
A private utility is any buried line owned by the property owner rather than by a public or regulated utility company. On a typical commercial, industrial or campus site, private lines can easily outnumber public ones. Common examples include:
- Electrical feeds from the meter or transformer to buildings, parking lot lighting, signs and gates
- Water service lines after the meter, irrigation mains and fire sprinkler supply lines
- Gas lines running from the meter to outbuildings, generators, pool heaters or kitchens
- Sewer and storm laterals, roof drains and French drains
- Telecom, fiber and security cabling between buildings
- Fuel lines, underground storage tank piping and EV charger conduits
- Abandoned lines that no one remembers but that are still in the ground
Why Private Lines Are So Often Missed
There are several reasons private utilities cause more than their share of damage.
No record keeper. Public utilities maintain mapping systems. Private owners often have only the original construction drawings, if they have anything at all. After decades of renovations, tenant changes and repairs, those drawings rarely match reality.
Non-standard installation. Private lines are frequently installed by different contractors over many years, at inconsistent depths, sometimes without warning tape or tracer wire.
Material choices. Modern private installations use a lot of PVC and polyethylene. Plastic pipe cannot be traced with a standard electromagnetic locator unless a tracer wire was installed and is still intact.
False confidence. Once the one-call markings are on the ground, crews tend to assume the site is clear. The unmarked private line becomes invisible precisely because everyone thinks the job was already done.
How Professional Scanning Finds Private Utilities
No single tool finds everything. Reliable private utility locating combines several methods and cross-checks the results against visible surface features.
| Method | What It Detects Well | Limitations |
|---|---|---|
| Electromagnetic (EM) locating, direct connection | Metallic pipes and cables where a transmitter can be clamped or connected at an access point | Needs a metallic path and an access point |
| EM induction and passive sweeps | Live power cables and metallic lines with no access point | Signal bleeds onto nearby lines, can confuse congested areas |
| Ground penetrating radar (GPR) | Metallic and non-metallic pipes, conduits, voids and tanks | Depth drops sharply in wet clay and highly conductive soils |
| Sondes and traceable rodders | Plastic pipes, drains and ducts that can be accessed from a cleanout or manhole | Requires physical access into the pipe |
| CCTV pipe inspection with sonde | Route, condition and junctions of sewer and storm lines | Only works in pipes large enough for the camera |
| Vacuum excavation (potholing) | Exact position, depth, size and material of a line | Point verification only, not a sweep method |
A skilled technician starts by walking the site to identify every surface clue: meters, valve boxes, cleanouts, light poles, transformers, backflow preventers and patched pavement. Each clue suggests a line that must go somewhere. The technician then uses EM tools on everything that can be connected, runs GPR sweeps across the work zone to catch non-metallic and unexpected targets, and marks the results in paint and flags using standard color codes. For critical work, the findings are surveyed and delivered as a drawing.
When Private Utility Scanning Is Essential
- Installing EV chargers, solar carports or new light poles in existing parking lots
- Adding fencing, signs or bollards with drilled post holes
- Building additions, patios, pools and landscaping projects
- Soil borings and environmental monitoring wells
- Saw cutting and core drilling through slabs on grade
- Any trenching on campuses, hospitals, airports, factories and data centers
For owners and general contractors who need a dependable partner, specialists in underground utility scanning such as MAYA Global Group combine multi-channel GPR with electromagnetic methods to map both public and private networks before excavation begins.
What to Ask Your Locating Provider
- Which methods will you use, and how will you handle non-metallic lines?
- Will you provide a written report or drawing, or only paint marks?
- How do you indicate confidence or uncertainty in what you mark?
- Do your technicians hold recognized training or certification?
- Do you carry professional liability insurance for locating work?
- Can you verify critical crossings by vacuum excavation?
Frequently Asked Questions
Does 811 mark private utilities?
Generally no. One-call centers notify member utilities, which mark the facilities they own. Lines past the meter or owned by the property owner are usually the owner’s responsibility to locate.
Can GPR find plastic pipes?
Yes, in favorable soil conditions. GPR detects changes in the electrical properties of the ground, so it can see plastic pipes, but its range is reduced in wet clay and saline soils. That is why it is used alongside other methods.
How long does a private utility scan take?
A small commercial site can often be scanned in a few hours. Large campuses or congested industrial sites may take several days, especially if a surveyed drawing is required.
Who is liable if an unmarked private line is hit?
Liability rules vary by jurisdiction and contract, but the excavator and the property owner are commonly exposed. Documented professional scanning is one of the best ways to show due care.
Conclusion
A one-call ticket is necessary, but on most commercial sites it only tells half the story. The private half, the lines owned by the property itself, needs its own investigation. A few hours of professional scanning costs far less than a severed feeder cable, a flooded trench or an injured crew member, and it gives everyone on site an accurate picture of what is really underground.