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 through dirt and help dig faster. However, if you step back and examine all the time factors involved with utility location, you can see that there are times when digging with 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.

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, and an operator needs to drive far distances to fill up.

Larger hydroexcavation units hold around 1,300 gallons of water, whereas smaller units can hold as little as 350 gallons. So even with the larger water tanks, you likely get between three and 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 need water and almost always go the entire day without needing to be refilled. It is nice to have some onboard water when challenged with a difficult dig spot but it’s not always necessary. If your water source is close by, this would be a nonfactor. However, if you are driving a distance to reach a water source, it could point towards air excavation being a better alternative.

Similarly, the added travel to dump your debris tank can be a long and costly process for hydroexcavation. Debris from hydroexcavation can rarely be used as backfill because of its slurry form and therefore it must be dumped at a different location. Air excavation debris is dry, can be used as backfill and dumped directly back into the same hole. Again, if your debris dump location is close, this could be a nonfactor. If your dump location is a long distance away, air excavation may prove to be the better alternative. 

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. 

If you have a very large area (or several large areas) to dig, water will drive faster results. Digging faster, as well as the large debris tanks commonly found on hydroexcavation units, will help negate or reduce some of the hydroexcavator pitfalls such as travel time to dump sites and to water sources when excavating larger areas.

Each project is unique, so 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 your 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 alternative.

Regardless of which application you prefer, Rock Equipment Sales & Rentals has the unit you need. Offering used and rental equipment with financing options available, Rock Equipment has equipment on-hand for immediate delivery. All available equipment can be found at www.rock-equipment.com.