Every day, operations up and down the west coast have to choose between air and hydro excavation when tackling their next dig. But are they choosing the right method for the type of soil they’re working with, and are they keeping in accordance with the local ordinances? Making the right decision between air excavation vs. hydro excavation can save your operation significant time and money.
Air Excavation: Pros & Cons
Air excavation is the best method only in specific situations and where legally permitted. Air excavators deploy compressed air to disturb and break up the native soil, and then utilize a vacuum tube to remove the dry spoils from the recently excavated area. The main benefit of air excavation is that since the spoils are dry, the crew is able to use them as backfill. This can reduce costs because backfilling with the excavated soil reduces the amount of spoils that need to be hauled off at the end of the day. Generally, the majority of spoils dug up can go back into the hole, and any leftover dry spoils are accepted at most dump sites. When using an airvac, the crew has the ability to run air tools like breakers & tampers, which allows a smaller crew to remove the asphalt or concrete surface and then make the soft dig with the air excavator.
However, the biggest challenge with air excavation is the method’s slow rate of digging and poor effectiveness in many soil types. Air excavation is least effective clay, shale, and hard pan soil. The second biggest challenge for this method is the dust and debris that is created at the point of excavation. Compressed air blowing dry soil can make for a very dusty job site, which a lot of cities and counties will not permit.
Hydro Excavation: Pros & Cons
Hydro excavation is a more universally applicable and legal method for excavating. This method utilizes pressurized water to erode the native soil, and the vacuum tube then removes the wet spoils from the hole. This is the preferred and most widely accepted method of soft dig, primarily due to its speed and effectiveness. Hydro excavation is effective in most soil conditions and does not create a dusty work environment.
The biggest challenge for hydro excavation is handling the spoils once the tank is full. A full spoils tank turns a hydrovac into a dump truck. The wet spoils are typically not allowed to backfill the holes, so slurry or backfill material will need to be brought out to the jobsite. Also, the wet spoils will need to be off-loaded at the end of the day, so an approved dump location is required?which can increase the cost of operation. However, these costs are typically offset due to the increased amount of work a hydrovac can complete in a single workday, which far exceeds the amount of work that can be completed with the air method in every soil type.
Which Is Right For You?
Air and hydro excavation are typically not interchangeable, though you may see hydro excavation utilized to break thru the hard surface and then air excavation used to complete the dig.
In conclusion, hydro excavation is the most popular vacuum excavation method for almost all soft dig applications, primarily due to the fact that it works 99% of the time for most soil types. The only soil type hydro excavation doesn’t work with is solid rock; however, no “soft dig” method works in solid rock formations. Air excavation is mostly used in soil types like sand or lightly compacted dirt and in areas where dump sites are limited, where hauling spoils off-site and hauling backfill materials to the job are cost-prohibitive.