Hydro vs. Air Excavation: The Perfect Machine for Your Application

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Hydro vs. Air Excavation: The Perfect Machine for Your Application

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Only a fool would claim that in a side-by-side single-hole dig comparison, air excavation would be faster than hydroexcavation. Water will always cut faster and help dig faster. However, if you take a moment and examine all the time factors involved with a given project, in some instances, air might be a better or faster alternative. Here are a few of the factors that might determine when it would be best to use air or water for an excavation project.

Hydroexcavation

Travel time to get water for hydroexcavation

At the start of the day (or end of the previous day) a hydroexcavator unit must be filled up with water. The refill process can take even longer if water is not available nearby, instead leaving an operator to drive far distances to fill up.

Larger RAMVAC hydroexcavation units hold around 1,300 gallons of water, whereas smaller units can may only carry up to 350 gallons. So even with the larger water tanks, you likely get three to five hours of hydro dig time before you run out of water. Now comes the big challenge: How far away is a water source to your job site? If you are lucky, your daily fill source is close by. If not, a lot of time can be spent traveling back and forth to get water for a hydroexcavation job.

Meanwhile, air excavation units rarely require water and can almost always go an entire day (sometimes a week) without needing to be refilled. Having a small amount of onboard water is helpful when challenged with a difficult dig spot but is not always necessary. If your water source is close by, a hydroexcavator will be your chosen tool; however, if you are driving a distance to reach a water source, it could point towards air excavation being a better alternative.

Air Excavation

Air excavation units like the RAMVAC AX are better capable of pulling up dry debris and all debris can be used to backfill holes once locate is complete, returning the ground to its original state. 

Photo courtesy of Wantman Group Inc.
Photo courtesy of Wantman Group Inc.

Travel time to debris dump site

Similar to the water source location, traveling to a dump location can be a long and costly process that is a result of hydroexcavation. Debris from hydroexcavation can rarely be used as backfill because of its slurry form and therefore must be dumped at a different location. Air excavation debris is dry, can be used as backfill and dumped directly back into the ground. If your debris dump location is close, hydroexcavation will be your go-to equipment every time; however, if you must travel a distance to reach a dump site, air excavation may prove to be the better alternative.

Does the project require you to backfill?

Understanding the scope of the project is an important factor in determining whether to dig with air or water. When do you get paid? Is it after the hole is dug and fenced off? Is it after the hole is dug, utilities exposed, repaired, documented and the hole returned to its original condition? As discussed, debris from air excavation can be immediately used for backfill, while hydroexcavation may require extra time and costs to haul backfill material to the job site to backfill holes.

How large of an area is being excavated?

If you have a very large area (or several large areas) to dig, water will drive faster results. Choosing a hydrovac with a large debris tank can help negate or reduce some of the above previous hydroexcavator pitfalls such as travel time to dump sites and to water sources when excavating larger areas.

Hydroexcavation is also generally preferred when digging in cold-weather climates, as it may require the use of hot water to cut through frozen ground.

What is the bottom line?

Each project is unique, but what is the better method, air or water? If you have a large area to excavate, can dump on-site, have a close water source, and do not have to backfill then hydroexcavation is the obvious choice. If you are digging small test holes, need to backfill when complete, and do not have a local spot to dump or fill with water, then using air excavation would likely be a better option.

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