Potholing for Utilities – Guide to Safe and Efficient Utility Locating

Potholing, also known as daylighting, is the non-destructive practice of digging a small, precise test hole to physically locate and visually confirm the exact position of underground utilities. This process is the most reliable way to prevent catastrophic damage to buried infrastructure like gas lines, fibre optics, and water mains. It’s a critical safety measure performed before any major excavation, drilling, or construction project begins, moving from an estimated location to a confirmed one.

For maximum safety, precision, and speed, especially in congested areas with sensitive utilities, vacuum excavation (hydrovac) is the superior method. Manual potholing is a viable, lower-cost option for shallow utilities in soft, easily accessible soil where machinery isn’t practical. Check out our Project Manager’s Guide to Hydro Excavation for more details.

When choosing between manual/mechanical potholing and vacuum excavation, consider these key differences:

Choose Manual Potholing for:

• Landscaping projects
• Verifying shallow irrigation lines
• Areas inaccessible to trucks
• Small residential projects with limited budgets

Choose Vacuum Excavation for:

• Urban construction sites
• Verifying gas and fibre optic lines
• Projects with tight deadlines
• Confirming multiple utilities
• Working near critical infrastructure

Ask yourself these questions to determine the best method:

1. Is the project in a congested urban area? If yes → Use Vacuum Excavation
2. Are there critical utilities like high-pressure gas or fibre optics? If yes → Use Vacuum Excavation
3. Is the soil soft and the utility shallow (less than 1.2 metres)? If yes → Manual Potholing may be sufficient
4. Do you need to verify multiple utilities quickly? If yes → Use Vacuum Excavation

The process involves five critical stages: legally notifying authorities through “Before You Dig Australia” (BYDA), reviewing utility maps and marking the surface, carefully excavating with non-destructive tools like a hydrovac or air spade, visually identifying and documenting the utility’s depth and position, and safely backfilling the hole.

• Contact “Before You Dig Australia” at least 2 business days in advance
• Obtain all necessary permits for excavation from local councils
• Review all provided utility maps and plans for the location
• Coordinate with utility owners for on-site marking

• Walk the site to identify visible signs of utilities (manholes, valve boxes, markers)
• Wait for all utility owners to mark their lines with paint or flags
• Mark your proposed pothole locations with white paint
• Document the marked areas with photographs

• Use a vacuum excavator as your first choice
• If vacuum excavation isn’t possible, use an air spade or hand shovels
• Never use a mechanical excavator within the tolerance zone (450-600mm) of a marked utility
• Keep the test hole as small as practical (typically 300mm x 300mm)
• Remove spoil to a designated area away from the work zone

Once the utility is exposed (“daylighted”):

• Visually confirm its type (PVC pipe, steel pipe, conduit, etc.)
• Measure the exact depth from the surface to the top of the utility
• Measure its horizontal position relative to a fixed landmark
• Take clear photographs from multiple angles
• Record all measurements in your project documentation
• Note the utility’s condition and any visible damage

• Backfill the hole in layers (“lifts”) of 150-200mm
• Compact each layer to prevent future settling
• Use appropriate backfill material (often the original soil)
• Restore the surface to its original condition
• Document the completed restoration

Mistake: Assuming the paint marks are exact.
Solution: The marks are approximations within a tolerance zone. Potholing finds the actual location.

Mistake: Using a backhoe or mini-excavator to save time.
Solution: This is the leading cause of utility strikes. Only use non-destructive methods near marked lines.

Mistake: Skipping the documentation step.
Solution: Proper records protect you legally and help future workers.

Potholing is a targeted excavation method used to precisely determine the horizontal and vertical position of underground utilities. Unlike slot trenching (which creates a continuous narrow trench), potholing involves creating small, strategic holes for visual verification, serving as the final, crucial step in damage prevention before construction or excavation begins.

According to industry data, a utility line is damaged every few minutes across Australia, with many incidents occurring despite proper notification to Before You Dig Australia. A significant percentage of these incidents could be prevented by adhering to safe excavation practices like potholing to confirm utility locations.

Potholing bridges the critical gap between “thinking” you know where a utility is based on records and “knowing” exactly where it is based on visual proof. This knowledge is the foundation of a safe and efficient project.

Potholing is essential before:

• Drilling piers for new buildings
• Installing fences, light poles, or signage
• Horizontal directional drilling (HDD) for new conduits
• Any roadwork involving grading or excavation
• Installing underground storage tanks
• Planting large trees in developed areas
• Building retaining walls
• Installing swimming pools

Hitting an underground utility can result in:

• Service disruptions affecting thousands of customers
• Expensive repairs and project delays
• Legal liability and regulatory fines
• Serious injuries or fatalities
• Damage to your company’s reputation

Potholing isn’t just a regulatory requirement, it’s a fundamental safety practice that protects workers, infrastructure, and communities. Whether you choose manual methods or vacuum excavation, the key is to always verify utility locations visually before any major excavation work begins. The extra time and cost invested in proper potholing pays dividends in avoided disasters, project efficiency, and peace of mind. Wilken have been providing potholing for utilities services for years, contact us today to discuss your project.