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The Best Way to Tackle Utility Potholing

The Best Way to Tackle Utility Potholing

Underground utilities present a major hazard for work crews. Digging without knowing the precise location of utility lines is challenging and dangerous. Thanks to new excavating methods, like potholing, utility lines, workers, and project sites are safer.


This excavation process, which is sometimes called ‘daylighting,’ includes making a series of small test holes in order to accurately locate underground lines. Potholing utilizes vacuum excavation equipment to verify the location of subsurface lines or other obstructions in or around an expected bore path.

Potholing can tell workers a lot about buried utility lines, including:

  • Horizontal position,
  • Depth,
  • Type of line, and
  • If there are any signs of damage to it.

These days, more work crews are regularly using potholing to avoid hitting water, electrical, gas, telecommunications, and fiber optic lines and help keep projects within budget and on schedule. It is also an effective technique for applications requiring boring holes, such as:

  • Installing signage,
  • Placing telephone or utility poles, and
  • Posting fences.


When potholing, utility crews use a portable vacuum excavator. First, test holes, usually measuring 6 to 12 inches deep, are made along the line where they plan to dig or begin construction. They excavate soil with high-speed suction straight down until the utility line is partially uncovered.

Both air and hydro vacuum excavation can be used for potholing. These methods utilize pressurized water or air to quickly move ground contents out of the way. This allows operators to have a clear view of subsurface features.

Hydro and air vacuum excavation safely dig even through hard, compacted dirt, rocky soil, and clay. Unlike the traditional methods of using a shovel or heavy equipment, it won’t cut a utility line hidden below the surface. Vacuum excavation is a non-invasive, non-mechanical, and non-destructive process. Potholing with vacuum excavation simply uncovers the line, leaving it intact, without damaging or moving it. Plus, when compared to these other methods, vacuum excavation leaves a smaller site footprint and decreases the time needed to finish the job.

Then, displaced dirt and rock debris is suctioned away from the excavation area through a large hose. It is stored in a holding tank on the truck. Excavator trucks with different capacity tanks can be used to fit the size of the job. Once the lines have been accurately located, accumulated wet or dry soil which was removed during the digging process can be replaced as backfill.


For example, cables and pipes installed using horizontal directional drilling (HDD) present extra challenges for work crews. Because this method doesn’t disturb the soil around the line or leave a traceable ditch line, it can be harder to see where the line runs. The ground around the line remains hard and requires more force to dig through it. Digging blindly or using more force near a cable or pipe make the excavating job very risky.

Yet, when working near the tolerance zone, contractors need to verify exactly where underground lines lie. Because of its non-invasive nature, air and hydro vacuum excavation can be used to dig within this zone to uncover the lines. This is because vacuum excavation is significantly safer than digging with shovels, backhoes, or other invasive equipment made of metal.

The information gained from potholing allows excavation and construction projects to proceed without the fear of striking any underground feature. Potholing is much more accurate and fast than relying on charts and utility maps which may be incorrect or out of date. In all, potholing helps avoid, if not eliminate, the following:

  • Life-threatening accidents,
  • Damaged underground utility lines,
  • Service interruptions and outages,
  • Equipment damage,
  • Costly repairs,
  • Contractor fines,
  • Liability issues and
  • Frustrating project delays.


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TPM Group
1731 River St
Bowling Green, KY 42101