Hydro excavation is the process of excavating utilizing a combination of pressurized water and a high-powered vacuum system to remove the resulting spoils.
This type of digging allows for excavating to find buried infrastructure without the risk to any underground pipe or cable.
A Brief History of Hydro Excavation
Hydro excavation technology has been widely accepted in western Canada for over 20 years. The first expansion move for this type of excavation was almost entirely in the oil and gas sector. As safety became more and more of a priority in the energy sector, the use of these hydrovac units gained momentum, but primarily in the western Canadian oil and gas industry.
Any line strike in trenchless construction and rehabilitation posed such an obvious safety and environmental risk that not using hydro excavation once it was available was tough to do.
After several years, the movement began to spread to eastern Canada and south into the United States. It took some time to create the same demand for the process as it was initially viewed as an added cost by contractors.
As time went by, other industries including telecom, electrical and municipal began to focus heavily on damage prevention. Hydro excavation slowly gained traction and applications were added.
How is Hydro Excavation Used Today?
As we fast forward 20 years, the industry is certainly mainstream in Canada. It's no longer questioned as whether or not it should be used when working around underground facilities. It's just done.
In certain American markets it is beginning to gain the same sort of acceptance, however the US market as a whole is perhaps 10 years behind Canada when using truck volume to population as a measuring tool.
How are Hydrovac Trucks Being Utilized?
As experienced construction professionals saw these hydrovac trucks work, applications have constantly been added to the list of tasks these trucks can perform efficiently.
- Visual utility locating.
- Slot trenching.
- Piling holes.
- Elevator shaft clean-outs.
- Tank cleaning.
- Remote excavations where conventional equipment cannot access. For instance the inside of buildings, backyards, etc..
- Power pole holes.
- Bore mud removal.
- Micro-trenching debris removal.
What Challenges Does Hydro Excavation Face?
As the Hydrovac units became more prevalent, much of the work was in urban areas. Obviously, underground cables and pipes are most dense where the people live. With this move other challenges have emerged in this industry.
One is the offloading of the spoils.
A Hydrovac that has excavated in average conditions ends up with a tank full of spoils that need to be offloaded. Initially many facilities would accept this product for a price, however as time goes on and truck density increases, these facilities in many jurisdictions require licensing which has limited the locations where dumping can occur.
An equally important issue related to the spoils is that these trucks, as initially designed for the energy sector, are generally too heavy to travel down city roads fully loaded enroute to disposal. This has resulted in many fines, liability and trucks running at less than capacity to protect against the risks of running heavy.
This liability could extend all the way from the operator of the truck, to their employer and perhaps even where the product came from.
How Can Hydro Excavation Improve?
One solution to both the dumping and the weight issue is to try to excavate with compressed air as opposed to water.
Air excavating also allows the fill to possibly be used on the same job site. It is often difficult to use it to backfill or locate holes for compaction reasons, but it certainly faces less offloading challenges than water. In some soils—primarily those that are porous—the air approach can be effective.
Where soil content is non-porous to some degree or frozen air will be inefficient. Air certainly has effective applications but has not been accepted as a full-time alternative to water.
There's been a movement in certain markets where certain products are added to the hydro excavated product to solidify the product to open up more dumping options. These include corn byproduct, polymers and other solidification product.
When these can be utilized often the material can be dumped in many places because it will not flow when dumped. There is no current system integral to a truck that allows for this to be done in an efficient manner.
Final Thoughts
It would seem that the bottom line is that the industry really likes the excavating properties of water. It is efficient in all soils. It can cut through frost.
However finding creative ways around the challenges of the spoils and resulting truck weights is a work in progress.
The concept of safe excavating is certainly here to stay. The underground continues to become more cluttered. The prevalence of fiber optics and the cost of damage to that infrastructure require every precaution to be taken.
Additionally, as directional drilling has become popular, assumed depths of utilities are less likely to be accurate in all cases and visually confirming crossings has become a must.
Line strikes continue to be a reality and two dimensional locates are an excellent starting point, but the only way to know for sure where the line is located is to see it.