From Trenchless Technology.
As horizontal directional drilling (HDD) projects become more prevalent for installing utilities in congested urban areas, vacuum excavation plays a crucial role in ensuring safe and efficient
operations. However, as with any underground construction project, proper procedures and safety protocols must be followed to mitigate risks and prevent costly damages or injuries. And with today’s increasingly complex underground environment, there is no room for error.
This is where vacuum excavation shines – offering a non-destructive and precise method for exposing and locating underground utilities before and during the HDD bore. To maximize jobsite safety and productivity, following vacuum excavation best practices is essential to mitigate risks, prevent costly damages and protect HDD crews.
Here are a few key vacuum excavation safety considerations HDD professionals should follow to ensure a successful HDD jobsite
Prep Work: Understanding Ground Conditions
Thorough preparation begins by evaluating soil conditions at the jobsite. Local dealerships can often provide valuable insight into typical ground conditions for the area. This information guides the decision between air excavation for softer ground conditions like sand and topsoil versus hydro excavation’s suitability for denser clay, rock or other compacted formations.
While hydro excavation is generally the more efficient choice, it requires access to water and liquid spoils disposal, which can impede productivity. Air excavation alleviates those needs but may progress slower in harder soil types. Many contractors leverage a combined approach, employing air excavation for surface removal before transitioning to hydro excavation as complexity increases at deeper levels.
Nozzle Selection and Techniques
Once the appropriate excavation method is determined, contractors must follow nozzle best practices to ensure jobsite safety. A rotating nozzle, also known as an oscillating nozzle, is the only nozzle that should
be used for exposing utilities. This type of nozzle does not have a direct spray which can damage utilities. Also, it delivers a constant stream of circulating water that pulls away more dirt and can use up to 50 percent less water than a fan nozzle. Essentially, the oscillating water stream maintains safety without sacrificing productivity.
Nozzle distance from the utility is also critical. Operators should keep the spray nozzle 8 inches from the ground or utility that is being exposed. Holding the nozzle closer than 8 inches or directly applying the excavator to a certain area could cause damage to an existing utility. It’s also important to never use the nozzle as a shovel or pry bar. Putting the nozzle into the dirt can cause damage to the wand and result in
costly downtime. If an operator is struggling to excavate through hard soil or heavy clay, they should use a hot water heater rather than moving the nozzle closer.
Pressure Regulation
Operators should also be mindful of their water or air pressure. For hydro excavation situations, the recommended pressure for soft excavation is no greater than 2,800 psi, while an air-excavator should
stay below 300 psi. Although many vacuum excavators and nozzles offer higher psi capabilities, too much pressure can damage utilities and other underground infrastructure. The pressure should be reduced even further if using heated water.
Hot water heater packages can help break down soil without applying additional water pressure. However, water temperature should stay below 150 F.
As a best practice, operators can also consult the utility owner if they are using a vacuum excavator to expose utilities, as they may have their own requirements for using hydro or air excavation.
For example, some gas line owners recommend using a maximum of 2,200 psi when exposing their utilities with a hydro excavator to prevent any damage.
Maintenance Fundamentals
Apart from excavation procedures, simple maintenance protocols go a long way toward uptime. One of the biggest selling points of vacuum excavators is that they have minimal maintenance requirements — and the ones they do have are simple. Manufacturers are designing their vacuum excavators to eliminate daily maintenance and grease points, allowing operators to focus on their job site tasks.
The most important daily maintenance task for operators is to always dump and clean the debris tank and empty the freshwater tank at the end of every day. This prevents complications that could limit vacuum excavator productivity.
Another maintenance best practice is to routinely check cyclonic, debris and water filters, as obstructions can reduce the suction power and water pressure of the machine.
Leading with Efficiency and Safety
Ensuring the safety and integrity of underground infrastructure is paramount in any HD project. Proper exposure and vacuum excavation techniques are the foundation of avoiding damage to these critical utilities. By embracing vacuum excavation best practices, operators can not only boost their efficiency but also significantly enhance jobsite safety. Success on the HDD jobsite hinges on a thorough understanding of the varied ground conditions, proper machine maintenance and effective utilization of PSI and nozzle selection. By mastering these aspects, operators can confidently pave the way to a safe and successful project completion.
Chris Thompson is vacuum excavation product manager at Ditch Witch.
