What Is Utility Potholing?

October 26, 2023

Utility potholing can be used to (safely) expose underground utilities such as pipes, cables, and other infrastructure. In this article, we'll look at methods used for potholing, its benefits, and the costs associated with this essential procedure.

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Potholing methods
Benefits of potholing
The potholing process
How much does potholing cost?
Potholing: an essential step

Potholing: locating underground utility lines

Potholing, also known as utility potholing or daylighting, is a process used to locate underground utility lines. It involves making small test holes to gather information about the buried lines, such as their horizontal position, depth, type, and any signs of damage. Work crews often use potholing to avoid hitting water, electrical, gas, telecommunications, and fiber optic lines — helping to ensure that projects stay within budget and on schedule.

Potholing is a highly precise method of utility location compared to other techniques, such as utility mapping and electromagnetic (EM) methods. While costly in both time and labor, it is essential — according to a recent DIRT report from The Common Ground Alliance, in the majority of damages attributed to excavation practices, a failure to pothole is a primary factor.

It can also be used for other purposes, such as digging holes to install signage, placing telephone or utility poles, and posting fences.

Po‎tholing methods

The two most common potholing methods are:

1. Vacuum excavation

Vacuum excavation is the most popular iteration of potholing because it's safer and non-invasive compared to other approaches. Using a vacuum excavator to shoot pressurized water (known as hydro excavation) or air, the locator digs small test holes until they find the utility line in question.

Because they use low-pressure water or air to remove soil through high-speed suction, vacuum excavators are the safest hands-on method for digging near utility lines because they minimize the risk of damaging underground infrastructure.

2. Hand digging

Breaking out shovels, picks, and other hand tools for some good old-fashioned digging is still a reliable method for potholing. While it may be slower compared to other methods, hand digging allows for greater control and precision, making it ideal for smaller-scale projects.

Be‎nefits of potholing

Potholing offers some notable benefits that make it a better choice in some situations than other utility location methods. Here are some key advantages:

1. Preventing accidental damage

Construction crews can use potholing techniques to locate and identify underground utilities with great precision, reducing the risk of accidental damage during excavation. This helps prevent costly repairs, service disruptions, and potential safety hazards.

2. Ensuring worker safety

Potholing helps workers gain a clear understanding of the underground infrastructure they are working around. This knowledge empowers them to take necessary precautions and avoid potential hazards on the job.

3. Minimizing project delays

When crews know the exact location of underground utilities, construction projects can proceed smoothly — without unexpected delays or costly setbacks.

The potholing process

The potholing process involves several steps:

1. Planning and research

Prior to venturing into the field, it's important for crews to spend time on planning and research. This includes reviewing utility maps, obtaining necessary permits, and identifying potential risks or challenges.

2. Marking and locating utilities

Using utility maps and specialized equipment, construction crews mark and locate the underground utilities in the designated area. This step ensures accurate excavation and prevents damage to the utilities.

3. Selecting the right method

Based on the project requirements and site conditions, project stakeholders select the best potholing method. Factors such as soil type, utility depth, accessibility, and even weather play a role in determining the most suitable technique. For example, if the ground is frozen, crews can use heated water in a hydrovac to thaw soil and remove it more easily.

4. Excavation and exposure

Once the utilities are marked, and the method is chosen, the actual excavation process begins, usually starting with small test holes around one foot in diameter. After the line is located, workers expand the width and depth of the holes to investigate the route of the pipe or line in relation to the intended construction project.

5. Documentation and reporting

Following the potholing process, crews must complete detailed documentation and reporting, including recording location, depth, and condition of the exposed utilities, which can be used for future reference and planning.

Ho‎w much does potholing cost?

The cost of potholing varies depending on factors such as the size and complexity of the project, chosen method, and the location — but it's never an economical option. At an average cost of up to $2,000–5,000 per hole, potholing is best reserved for situations where you need to find out the exact placement of a utility line.

But considering the potential savings in terms of preventing utility damage, avoiding project delays, and ensuring worker safety, the cost of potholing is a worthwhile investment.

Po‎tholing: An essential step

Utility potholing is a vital process in construction and infrastructure development. Using low-impact tools such as hydrovacs, crews can safely expose underground utilities — helping to prevent accidental damage and injuries during construction projects. While the cost of potholing may be significant, it's a necessary investment to avoid costly repairs, project delays, and potential hazards.

Accurate utility mapping helps minimize the need for potholing because crews start out with better information. Instead of searching for a line, they're testing for the exact location of lines they know are present in a given area — helping them work quickly and efficiently, and cutting down on costs.


What does potholing mean in construction?

Potholing, also known as daylighting or test holing, is a construction technique used to locate and verify the presence of underground utilities before excavation or construction activities begin. It involves digging small, exploratory holes to expose and identify the utilities, such as water pipes, gas lines, or electrical cables, that may be buried beneath the surface.

How does a vacuum excavator work?

A vacuum excavator, also known as a vacuum truck or suction excavator, is a specialized machine used for digging and excavating soil or other materials using suction. It works by creating a powerful vacuum that sucks up the material from the ground and deposits it into a storage tank on the truck.

The vacuum excavator consists of a suction hose connected to a nozzle or wand that's inserted into the ground. The machine sends a high-pressure jet of air or water to break up the soil, create a slurry, and suck it back up through the hose.

Vacuum excavators are commonly used in construction, utility work, and other industries where precise and non-destructive digging is required. They offer several advantages over traditional excavation methods, including reduced risk of damage to underground utilities and faster excavation times.

Chris Garafola

With over a decade of experience spanning agencies and innovative startups, Chris is a dedicated content marketing leader, driven by the belief that content isn't just about consumption; it's about leaving a lasting impact on the person who engages with it. Inspired by 4M's mission to create the first online database of subsurface utilities in the U.S., Chris is eager to illuminate one of the infrastructure industry's most pressing issues and champion innovative solutions that deeply resonate with general contractors and civil engineers to address these challenges.