Vacuum excavation features roots dating back to the 1800s, when the mining industry began leveraging pressurized water as a safer, cleaner way to break up soil and dig. The method eventually took hold across the United States and Canada as a popular option at underground construction sites.

In the 1950s, modern vacuum machines were applied to cleanup and sewer applications. As the technology and equipment expanded to include both high-pressure water and air for digging purposes, vacuum excavation revolutionized the construction and utility industries. Today it is the preferred (and, in some areas, required) method for construction efforts like trenching, potholing and remote excavating.

In this article, we’re explaining the basics of vacuum excavation, visiting some reasons why it’s become so widely employed and discussing specific applications for construction.

What is vacuum excavation, and why is it so important?

In its most basic sense, vacuum excavation is the method of breaking up soil and vacuuming it out of the ground. Of course, the equipment used to accomplish this task, as well as the applications for which vacuum excavation is utilized, are much more complex. Even so, the entire process is applied with the intention of creating safer work environments, mitigating the risk of damage to underground utilities and creating cost efficiencies for construction and utility projects.

Here’s how it works: A truck or trailer-mounted vacuum machine, equipped with either a water or air source, pressurizes the source to dig deep and/or precise underground holes and then suction the debris out through a hose. It is a safer, quicker, more accurate and less risky alternative to traditional methods like hand digging or the use of mechanical equipment. It minimizes the disruption to buried infrastructure, thereby limiting the threat of danger or property damage posed by more abrasive and less precise options.

Hydro vs. air: how do these vacuum excavation methods compare?

As construction crews have increasingly opted for vacuum excavation as a means of keeping workers safe, minimizing risk and optimizing project plans, the technology has advanced and evolved. There continue to be important considerations for selecting the best deployment method, and understanding these factors is key.

Vacuum excavation is carried out via one of two pressure sources: water or air. Hydro excavation, which is also commonly referred to as hydrovac, hydro trenching or soft digging, is the method utilizing (often heated) streams of water to break up the soil. Air excavation, also termed airvac, pneumatic or air-knife excavation, leverages compressed air to break up the ground soil. In both cases, the debris from these digging methods is vacuumed out of the ground and stored in tanks for transport to a disposal site or for using as backfill later in the project.

Some of the identifying features of hydro excavation include:

• Ideal for lower-temperature and/or more compact soil conditions
• Fast, efficient, economical means of moving ground material
• Precludes the potential sandblasting that may occur with air excavation
• Minimal wear and tear on the vacuum machinery, as water is a natural lubricant

Defining characteristics of airvac excavation include:

• Unique ability to backfill dry soil and debris
• Easier to transport or dispose of material that’s not wet, muddy or heavy
• Less limited than water as a resource, and no need to “refill” during the excavation process
• More suitable for working around live electrical wires, as air is non-conducive

Understanding the distinctions between these two methods of vacuum excavation is essential to planning the project approach, which requires an examination of factors like project scale, resource supply, soil conditions, material backfill/disposal needs and underground hazards.

What are the specific applications for vacuum excavation?

Following are some of the construction and utility functions that vacuum excavation, given its characteristics and benefits, has become known for executing and optimizing.

Potholing
Potholing is a practice that construction teams should always be taking care to execute prior to digging so as to help protect workers, projects and underground infrastructure. Sometimes called daylighting, locating or subsurface utility engineering (SUE), potholing is a technique to garner visual confirmation of underground utilities, providing insight into their location, length and depth so workers can safely excavate around them.

The method involves digging a series of very small test holes, usually measuring 6 to 12 inches deep, and often leverages vacuum excavation to obtain the necessary verification of underground objects all along the project’s bore path. The water or air stream can cut precisely and efficiently through the soil, allowing for minimal material removal and safeguarding workers from dangerous risks like strikes on natural gas lines.

Trenching
There are different types of trenching for construction projects, and the variations are determined by specific work requirements. Whether you’re applying slot trenching, perimeter trenching, box trenching, linear trenching or another form, it’s about accurately digging to a certain dimension for that particular project.

Vacuum excavation by water or air source is commonly applied to trenching activities for its precision and safety advantages. It is especially valuable for slot trenching, or the process of digging narrow trenches for the installation of cables, lines or other systems. Hydro and air excavation enhance this process by mitigating accidental hits to underground utilities, which can result in costly damage, worker injury and/or prolonged service disruption. Vacuum excavation also necessitates less restoration effort than more conventional excavation methods.

Remote Excavation
One of the most beneficial aspects of vacuum excavation is that the equipment allows for easier access to remote, restricted or confined job sites. The water or air lance and the vacuum hose are the only pieces needed directly at the work location, which means the trucks and tanks can be positioned and connected at a distance.

When you have a project that involves narrow access roads, unstable soil conditions, low overhead clearances or similar obstructions and challenges, vacuum excavation is a major advantage. The tubes can be extended to accommodate hundreds of feet, preventing congestion and mitigating risk.

Debris Removal
In the context of construction work, debris removal is a significant undertaking. But with the technology of vacuum excavation, it can be managed in a faster, cleaner and more economical way. The vacuum hose suctions debris directly into a tank for storage. Depending on the needs of the project, the tanks can be transported to a disposal site for the contents to be removed, or they can be emptied back onto the job as backfill.

In some scenarios, wood pellets are employed to absorb, solidify and stabilize wet slurry from a hydro excavation effort. By transforming the liquified material to a more cohesive substance, pellets can make debris removal or backfill easier, cleaner and greener.

Ultimately, the non-mechanical nature of vacuum excavation renders it a softer and safer approach to a number of applications in construction and utility work. It is a prevalent option when precision and safety are priorities, and it remains a powerful, efficient practice for project teams.