Potholing Machines for Utilities 101

Potholing Machines for Utilities 101

Digging on the ground without knowing the exact location of underground utility lines is undeniably dangerous for work crews. Sure, there are utility locators such as electromagnetic location and ground-penetrating radar (GPR) that can identify and locate utility infrastructure underground, but there are instances where these are not enough to get the job done and you’ll need the help of private utility locating services.

In these cases, there’s a need to do potholing and excavating, which are the surest ways to know the exact location, size, and depth of some utilities. Utility locating services use several techniques like potholing, hydro excavation, and vacuum excavation—in order to find utilities underground, such as water lines,  and see their features.

Why these Techniques are Needed to Expose Utilities

The first reason is to follow local or state regulations which prohibit mechanical excavating within 18-36 inches of a marked utility line. This is necessary for the safety of the workers and other people on the job sites and the surrounding area.

There’s an incredibly high risk involved with working around utilities even when the excavators themselves have information on the location of the line.

Drawings and maps can become inaccurate, incomplete, or outdated and this is why safety regulations are kept in place. Workers’ safety is compromised when removing dirt and rock debris manually if they are using metal tools. They also have to deal with the possibility of unstable ground material that can collapse overhead.

The increased use of horizontal directional drilling (HDD) is also a factor. HDD reduces the number of road closures for utility installation projects and thus it’s being used increasingly to lay cables and pipes.

This drilling method also has less impact on the environment. But the downside is that HDD makes it harder for the GPR to locate utilities because of the process’s decrease in soil disturbance and the absence of traceable ditch lines, which are two features that GPR depend on.

So for areas where HDD was used, utility locators will have to resort to potholing and daylighting to locate underground lines.

What is Potholing?

Also called daylighting, potholing is the process of digging a test hole in order to locate and expose existing underground utilities while keeping the surrounding soil undisturbed.

This involves the potholing machine making a series of holes through soil, concrete, or asphalt. The workers will then use a vacuum or hydro excavation to remove the soil.

Potholing utilities can expose the positions and orientations—both vertical and horizontal—of the utilities and enable workers to check for damages such as cracks and punctures. Excavation potholing is also effective as a digging method for installing signs, utility poles, fences, and other jobs that would require setting posts in the ground.

Kinds of Excavation Process

As mentioned above, contractors use excavation to remove the dirt between the hole and the utility. Traditionally, workers would use hydraulic excavators on construction sites.

Nowadays, workers prefer daylighting excavation where utility lines are exposed through soft excavation techniques such as vacuum excavation or hydro excavation.

Hydro Excavation

This excavation technique uses pressurized water to move soil debris as well as rock debris out of the way. This entails the use of a long hose for suctioning the displaced dirt, water, and debris to a holding tank attached to a truck.

The workers will then haul the wet spoils away for disposal. This use of hydro excavators adds to the time and expense needed to complete the job.

Vacuum Excavation

This involves the use of pressurized air to break up compressed soil around the utility.  The workers will then vacuum the dry spoils and reused them as backfill. The vacuum mechanism may be able to utilize high-speed suction in light soils to remove the soil straight down until the utility is exposed partially.

Workers usually prefer using vacuum excavators, but they have to use hydro excavation machines in dealing with heavily compacted soils. The suction hose cleaner, with the help of water, can prevent the soil and excavated debris from gathering.

Equipment Used for Hydro and Vacuum Excavation

These two excavation types are usually worked on by a vacuum excavator or hydrovac truck. This one truck has high-pressure water and air excavation system, plus a water supply tank and a large tank that is designated to hold spoils vacuumed up from the site, as well as the drilling fluids. Some of the excavators are mounted on a trailer.

The hydrovac truck or trailer injects water under pressure into the soil using a wand or hose. The water pressure is strong enough to break up the soil but not strong enough to cause damage to the utility lines.

The soil is liquefied by the water and produces slurry. This slurry is carried by the vacuum to a tank attached to the truck. It’s the truck’s job to remove the slurry from the work site in order to keep it clean and orderly.

Benefits of Potholing and Daylighting Using Hydro or Vacuum Extraction

There are multiple benefits involved with using hydro or vacuum extraction for potholing and daylighting utility locations. First, they allow utility locators to ‘daylight’ utilities without the risk of damaging them because compared to mechanical excavating, they are less disruptive, less destructive, and less invasive. Also, these techniques have a less environmental impact and the site is easier to restore or repair after the job.

Since these two leave a smaller footprint compared to mechanical excavating, they reduce the time needed to complete a job. They can also be used in locations that cannot be accessed by traditional excavation machinery, plus the compact truck or trailer can operate easily in urban areas.

Hydro or vacuum extraction also eliminates life-threatening accidents and keeps projects progressing by minimizing delays. And most importantly, these two techniques won’t cut a utility line or other underground feature accidentally.

Choose the Right Utility Locating Services for Your Needs

If you’re looking for the best private utility locating services and mapping services in Southern California, you can’t go wrong with Util-Locate.

We are the No. 1 utility locating service and underground utility locator in Los Angeles, San Diego, Imperial, San Bernardino, Santa Barbara, Kern, Riverside, Orange, Ventura County, and all major Southern California cities.

To schedule a service with us, contact us at Util-Locate at (866)638-1075 today.