Potholing

Published: | Updated: August 20, 2020;

Definition - What does Potholing mean?

Potholing is an investigative construction method whereby the location of underground utilities is exposed. Potholing involves the drilling of exploratory holes, the depth of which spans from ground level to the required extent of the investigation. Potholing confirms the location of utility lines on site and any other existing structures that may be within the defined construction area.

Utility exposure is vital in both the construction and maintenance phases. During construction, there should be no conflicts that can result in potential damage to existing structures. In the maintenance phase, utility exposure through potholing is carried out to examine the utility's state to evaluate if there is any damage that requires remedial work or replacement.

Potholing forms a crucial part of horizontal directional drilling (HDD) exercises, as it allows for tracking devices to emit an electromagnetic field that finds hidden utility lines. This method avoids any utility lines in the drill area.

Once the utility is found on-site, it should be appropriately delineated, through the following means:

  • Using survey benchmarks and other features to tie in the location of the utility.

  • Measuring horizontal distances to permanent structures on-site and the vertical distance from at grade level to the utility.

  • Recording coordinates from GPS readings.

Potholing is also known as daylighting.

Trenchlesspedia explains Potholing

Potholing is the preferred method of finding underground utilities and structures. Typically, due to settlement or ground movement, the location of utilities tends to shift over time. Other methods of utility location, such as charts, maps, and as-built drawings, do not provide an accurate reflection of the position if there is ground movement. Potholing techniques eliminate the risks associated with incorrect utility locations.

Potholing Methods

There are three main potholing techniques used in the construction industry. Choosing which procedure is best suited depends on the scope of works to be carried out, the associated risk, and the project budget.

  1. Hand Digging

In this method, the excavated material is removed through hand tools, ranging from shovels to digging bars. Hand digging is not suitable for large operations as it is both time and labor-intensive. Small home projects or confined workspaces are instances where hand digging is preferred. An upside to hand digging is the limited cost as expensive equipment is not required.

  1. Backhoes

Now considered a risky potholing method, the use of backhoes was once the most popular potholing technique. Excavation with a backhoe is hazardous as utilities can be damaged during the exposure process. It is always essential that a spotter be present during potholing with a backhoe. The spotter is responsible for communication with the backhoe operator on the observation of any utilities. Backhoes are typically used in greenfield potholing operations, where the risk of interference with existing utilities is reduced.

  1. Vacuum Excavation

Vacuum excavation is the preferred method of potholing. It is non-destructive, accurate, efficient, safe, and cost-effective. Vacuum excavation is carried out in two ways, either by air excavation or water excavation. Depending on the chosen method, water or air is used to break up the soil. Once this is completed, a vacuum gathers the excavated spoil.

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