Soft excavation methods should be used in confined and higher-risk areas as this type of excavation is superior to mechanical excavation methods when it comes to accuracy, safety and efficiency. Discover all three methods in this article!
When excavation work is necessary, knowing what is hidden below is one thing, but choosing the right method is quite another. The power shovel may not always be the most appropriate tool since the nature of sites and work zones differ due to their location, shape, depth, type of backfill, time of year, but mostly the type of underground infrastructures that are hidden below. Sometimes, the excavation must be carried out in an almost surgical manner to locate and protect pipelines, conduits and underground cables adequately. The three soft excavation methods are hydro-excavation, vacuum excavation and… the good old hand shovel!
At least three (3) days prior to excavating, the first thing to do is to make a locate request to Info-Excavation. It is just as crucial to have in hand the answers from the owners of underground infrastructures for which Info-Excavation confirms that their infrastructures are located beneath the worksite. Once information is received, the location of underground infrastructures within the worksite must be validated. These markings indicate where to excavate while respecting the buffer zone, generally located one (1) metre on each side of the markings. If risks become significant and careful and precise excavation is required, using the appropriate soft excavation method may turn out to be critical.
“Depending on excavating conditions, choosing which of the three soft excavation methods to use becomes quite easy. Whenever it is deemed necessary, the use of such methods must not be neglected. Even today, unfortunately more than half of the damages reported happened because appropriate excavating methods were not used”, explains Nathalie Moreau, General Manager, Prevention and Public Affairs at Info-Excavation. Furthermore, the costs associated with these methods, naturally excluding the hand shovel, are much more affordable than in the previous decade: “Hydro-excavation or air excavation equipment was really expensive back then since they were considered as highly specialized equipment, but they are now very accessible. Believe me, it’s best for contractors to use these types of equipment than to pay for damages done to underground infrastructures, without forgetting the social impact they may cause”, adds Mrs. Moreau. “The point is, you don’t have to do all the excavation using these methods, but they could at least be used to perform exploration wells to physically locate and visualize underground infrastructures before excavating.”
Hydro-excavation is a non-destructive method that uses pressurized water and a vacuum system. It’s clean, fast and safe. Pressurized water is injected in the soil using a manual lance. It offers a means to precisely excavate while protecting underground infrastructures. Slurry made using this technique is then vacuumed out and stored in a tank. This method is quite efficient in highly congested subsurface and when excavating frozen ground, since water may be heated up to 45 degrees Celsius.
Air Vacuum Excavation
This technique also uses vacuuming to remove material around conduits and underground cables. Compressed air is used to protect infrastructures. The air pressure helps loosen dirt and soil that are then suctioned out through a vacuumed pipe. It’s an efficient method when excavating in non-loamy soils or unfrozen grounds. Furthermore, the backfill material can be used immediately if need be.
Obviously, it’s the slowest and least invasive technique. But, if conditions permit, it remains just as efficient as the ones described above. Adequate temperatures (unfrozen ground) and loose material such as gravel, sand and secondary backfill generally allow hand excavation. The greatest benefit of this safe method is that it generally provides an ongoing assessment of the work in progress and can be used in confined areas.