What Is Utility Potholing?
Utility potholing — also called service potholing, vacuum potholing, or test holing — is the process of creating a precise, targeted excavation to physically locate and verify the exact position and depth of a buried utility service. Where Dial Before You Dig plans tell you roughly where a pipe or cable should be, a pothole tells you exactly where it is.
The technique uses high-pressure water to loosen soil in a controlled column, with a vacuum system simultaneously removing material into a debris tank. The operator works incrementally — never forcing depth — until the service is physically visible. At that point, its horizontal location, depth, diameter, and material type can all be recorded and photographed.
GreenVac performs utility potholing across Canberra ACT, Queanbeyan, Bungendore, Goulburn, Yass, and throughout Southern NSW. The compact trailer rig accesses suburban lots, rear yards, and sites along tight service corridors where full-size vacuum trucks simply can't operate.
When Is Potholing Required?
Potholing is the correct approach whenever you need certainty about a service location before committing to work that carries consequences if something is in the wrong place. The most common triggers:
- Before trenching or boring across a known service corridor
- To confirm electromagnetic or ground-penetrating radar (GPR) locating results
- When as-built drawings are missing, inaccurate, or predate significant site works
- Prior to road construction, subdivision works, or large civil earthworks
- When multiple services are suspected in the same corridor at different depths
- For horizontal directional drilling (HDD) — bore path clearance requires confirmed service depths
- Insurance or project compliance requirements before excavation commences
- When working in Canberra's older suburbs where infrastructure records are patchy at best
In the ACT, utility corridors frequently carry multiple services in tight proximity. A gas main, water main, and NBN conduit may share the same easement corridor at different depths — and council or utility records may account for only two of the three, or record them at depths that don't match what was actually installed.
The Risks of Skipping Potholing
Assuming service location is one of the most common causes of utility strikes in Australian civil and construction work. The industry sees hundreds of incidents per year — and the majority involve situations where the location of a service was assumed rather than confirmed.
Work StoppageA utility strike triggers an immediate halt to all work on site. Regulatory investigation, emergency response, and repair coordination can extend stoppages for days.
Contractor LiabilityStriking an asset you could have confirmed and avoided creates a clear liability position. Utility asset owners pursue repair costs, and they have sophisticated claims processes.
Physical InjuryStruck electrical cables and gas mains pose direct risk of electrocution, explosion, and serious injury — to operators, tradespeople, and bystanders.
Third-Party ClaimsNBN outages, gas supply interruptions, and water service disruptions affect neighbours and businesses. Third-party claims follow directly from utility strikes.
AS/NZS Non-ComplianceAustralian Standards and WHS Regulations require documented service verification before excavation near utilities. Missing this step creates regulatory exposure.
Project Cost BlowoutEmergency repairs, reinstatement, dispute resolution, and extended site shutdowns routinely cost multiples of what a potholing program would have cost upfront.
Benefits of Hydrovac Potholing
Definitive Visual ConfirmationYou see the pipe. You know its depth, its diameter, its material, and its exact horizontal position. No assumption, no inference.
Safe for the Target ServiceWater pressure used for potholing cannot crush, shear, or cut steel, copper, polyethylene, or conduit materials when applied correctly. The service being located is not at risk.
Fast — Most in Under an HourA typical pothole takes 30–60 minutes. A day's potholing program across a trench corridor or subdivision provides the certainty needed to excavate with confidence.
Documented ResultsDepth, location, and service type can be photographed and recorded at each pothole for project documentation, compliance records, and as-built updates.
Compact AccessGreenVac's trailer rig reaches pothole locations that vacuum trucks can't access — in rear yards, beside fences, along footpaths, and in tight suburban service corridors.
Minimal Surface DisruptionA pothole is small by design. Reinstatement after a vacuum pothole is straightforward — far simpler than repairing the aftermath of a utility strike.
How Potholing Works in Practice
The GreenVac operator positions the vacuum hose and pressure lance directly over the target location — typically a point indicated by utility plans, locator marks, or GPR output. The pressure lance directs water at a controlled angle into the soil, loosening material in a column while the vacuum simultaneously extracts it into the debris tank.
The operator controls both rate and direction, working incrementally and stopping to assess progress. The process continues until the service is physically confirmed — visible, touchable, and measurable. From that point, the depth is recorded, the horizontal position noted, and the hole can be backfilled with the extracted spoil or with suitable fill material depending on the project requirement.
In Canberra's clay-heavy soils, the water pressure cuts cleanly. In sandier or loose fill conditions common in some Southern NSW sites, the walls of the pothole are managed carefully to prevent collapse before the service is confirmed.
Frequently Asked Questions
How deep can GreenVac pothole?
Most utility services in ACT and NSW are buried between 300mm and 1,500mm. GreenVac routinely works across this entire range. Services in older Canberra suburbs are sometimes shallower than expected — another reason physical verification beats paper plans.
How many potholes can be done in a day?
In typical Canberra ACT suburban soil, 4–8 potholes per day is a reasonable working rate, depending on access, depth, and spacing. Jobs with many closely spaced potholes along a single corridor are more efficient than scattered locations across a wide area.
Do I need to mark locations before GreenVac arrives?
If you have locator marks on the ground from a utility locating contractor, that's ideal — it makes the job faster and more efficient. If not, James can work from DBYD plans. The more information available upfront, the better the outcome.
Can potholing damage the service being located?
Correctly performed hydro potholing cannot crush, shear, or cut steel, copper, polyethylene, or conduit materials. The water pressure used to loosen soil is not sufficient to damage properly installed services when the correct technique is applied. This is a key advantage over mechanical potholing methods.
What if the service isn't where the plans say it is?
This happens regularly — particularly in Canberra's older suburbs. If the service isn't at the indicated location or depth, the search area is widened methodically. Finding it in the wrong place is still infinitely better than hitting it with a mechanical excavator.