With its ease-of-use, high ROI and soft-excavation style, vacuum excavators are growing in popularity across a wide range of industries and applications. Today’s contractors are using them to support HDD jobs, irrigation installation, and even landscaping and tree-care tasks. One reason for the growth is that present-day jobsites and underground environments are congested, with limited space and often many hazards. Vacuum excavators offer a solution to these problems.
But no two jobsites are the same. And, as the fiber market continues to grow and the need for utility rehabilitation continues to mount, vacuum excavators will be asked to conquer a wider range of jobsites – and that means a broader range of soil types.
WORKING FROM THE GROUND UP
There are five main ground conditions that vacuum excavator operators may deal with on a job: rock, sandstone, clay, topsoil and sand. The good news for fleet owners and operators is that these machines are versatile. But to be as productive as possible, contractors must first understand the jobsite and its ground conditions.
This is the first step to making the right machine decisions and starting down the path to success. Contacting the local dealer is the best way to find out this information. Ground conditions not only vary jobsite to jobsite, but they can change within one jobsite. It’s not uncommon for a vacuum excavation operator to begin their excavation through topsoil and suddenly come across clay. Local dealers have experience in this area and likely will be able to help determine what an operator will encounter on the job.
Operators should also look for visual cues, like changes in soil patterns, to determine ground conditions. Another tip is to observe the natural landscape; jobsites in a valley will often contain clay, while jobsites on a hill will usually have harder formations.
Once an operator determines ground conditions, they can then determine if they will need air or hydro excavation, their ideal water tank size and other strategic excavation choices. These are the five most common ground conditions and how to best approach them with a vacuum excavator.
Rock and sandstone are two of the most difficult soil types to excavate and, as a result, they take the most time. Operators facing rocky or sandstone conditions should use hydro excavation with hot water because it more effectively cuts through the difficult soil, just as hot-waterpower washers are utilized to clean construction equipment and used in many other applications. Contractors can get hot water onsite by using a boiler package, which is a diesel-powered water heater offered as an add-on by manufacturers. Best practices dictate that operators keep heated water at or below 130 degrees, but they should always check with the utility owner for their preferred technique or method.
More difficult conditions will necessitate using more water and potentially more trips to dump since the operator will be excavating for longer. Operators expecting rock or sandstone should invest in larger water tanks, be familiar with local slurry dumping regulations, and understand what the nearby water refill options are. Excavating through rocky conditions is also easier with a machine that has a higher horsepower and greater capabilities.
Clay is more easily excavated than rock and sandstone, which opens a few more options for contractors facing these conditions. First, clay conditions can be excavated with hydro or air excavation. Hydro excavation is typically the more efficient excavation method, but air excavation has its place. Since it is a dry excavation method, air excavation limits the complications related to slurry disposal and eliminates challenges related to finding a water source.
If an operator chooses to go with hydro excavation, clay will require less water and less time on the jobsite than rock and sandstone. Similar to rock and sandstone conditions, hydro excavation in clay conditions should be done with a boiler package.
Topsoil and sand are the least difficult soil types to excavate, but that doesn’t mean these ground conditions don’t have their own challenges. Jobsites with topsoil or sand can be sensitive and require a more delicate touch to avoid the ground cave-ins when excavating.
As with clay, hydro-excavation is usually the more efficient option with topsoil and sand, however due to the sensitivity of sand in particular, air excavation offers a more accurate option. Since air excavation doesn’t create slurry, it keeps more of the soil together and limits the chance of the hole caving in on itself. Contractors who are looking to ensure a clean hole or who are working on an extra sensitive jobsite – like a golf course – should opt for air excavation. Some municipalities even require air excavation to be the first option in sandy ground conditions.
For the contactor looking for the quickest way to get the job done, hydro excavation is the way to go. Hydro excavation in softer soil types will require less water than on jobsites with more difficult soil types, but topsoil and sandy conditions will lead to more debris being collected. Since less water is needed to excavate, less slurry is created, and more solid debris is gathered. Contractors who are using hydro excavation in softer soil conditions can invest in a more economically-sized machine for their expected workload, but they should make sure they know where water-refill locations are in case they encounter more difficult ground conditions.
In addition to choosing technology based on soil type, it’s important to follow general vacuum excavation best practices. This includes continuously moving the nozzle to avoid applying excessive pressure to one area, keeping the nozzle eight inches away from the utility being excavated to avoid harming it, and never using the nozzle as a shovel because it can cause damage. Lastly, vacuum excavation water pressure should always remain below 3000 psi.
A local dealer is always the best place to go with any vacuum excavation questions or needs.
Chapman Hancock is Product Marketing Manager – Vacuum Excavation with Ditch Witch. Visit ditchwitch. com/vacuum-excavation to learn more.