Hydrovac excavation is a trenching technique that involves loosening soil with a high-pressure water jet, while simultaneously removing the soil from the site via a high-powered vacuum. This technique is utilized on a wide range of infrastructure projects and is considered to be safer and more environmentally-friendly than other trenching methods.

However, while hydrovac excavation is a low-impact trenching method, as with any construction activity, this operation poses some inherent health and safety risks. Engineering and construction teams should, therefore, use appropriate equipment and develop health, safety, and environmental (HSE) plans well in advance of any trenching. It is crucial that teams work together to classify potential hydrovac risks and establish practical measures to mitigate them.

By taking the time to identify the risks and hazards of a project, construction teams can minimize the occurrence of events that can lead to work-related injuries and even fatalities.

Listed below are some of the best safety practices that should be implemented on a typical hydrovac job site.

1. Locate Underground Utilities

Hydrovac is a trenching construction activity; therefore, there is the possibility of inadvertently striking or damaging existing underground utilities. Some buried utilities, such as telecom cables, present little to no safety risk to construction personnel. At worst, damage to these types of infrastructure may be an inconvenience to affected areas.

However, depending on the job site's location, underground infrastructure may consist of potentially dangerous utilities, such as electricity lines and natural gas lines. Damage to these lines can lead to electrocution, fires, and explosions, which can result in worker injury or death.

Hydrovac job sites should identify the location of all buried existing utilities prior to commencement of work. In the United States, contractors are mandated to use the one-call hotline (811) before any digging operation. The nationwide service will inform utility operators with infrastructure near the site to mark their utilities with paint or flags.

In lieu of such a service, non-invasive locating techniques, such as ground-penetrating radar (GPR), X-ray, and electromagnetic location technology, may be used to identify existing buried utilities.

2. Use Proper Signage On Site

Using proper signage on a hydrovac job site involves placing relevant notices at workplace entrances and other areas they are likely to be seen. Proper signage not only alerts workers of potential hazards on the job site, but they also enforce safe working practices and encourage workers to identity and report hazards.

Depending on the location of the site, signs should:

  • Warn construction staff as well as the general public of various on-site hazards when entering or passing near the site.

  • Enforce the use of personal protective equipment (PPE) when entering the site.

  • Indicate "Danger" near the truck when excavations are in progress. This is particularly important when working in areas with exposed energized or isolated cables. These signs should be placed within 3 meters (10 feet) of the truck.

3. Ensure that Workers Are Trained

Personnel working on hydrovac excavation projects should possess adequate training in accordance with industry standards and recognized safe work practices. Workers should also be properly trained to use the equipment they are operating per the manufacturer's recommended procedures and guidelines.

On hydrovac job sites, the minimum recommended training requirements for on-site personnel include, but are not limited to:

  • OSHA training relevant to the construction industry.

  • Fall protection – If required, workers should be equipped with fall protection equipment, such as harnesses, depending on the project.

  • Traffic protection – Hydrovac operations often occur in areas near or within roadways. Therefore, construction personnel should be aware of the various safety practices that should be adopted when working in areas with active traffic. Hydrovac trucks, in particular, can be cumbersome and difficult to operate in high traffic areas. Some trucks, such as those by Rival Hydrovac, are equipped with systems that make it easier to maneuver the vehicle in tight or busy roadways. Rival’s dual back up cameras increase all-round visibility, improving safety during truck operation.

  • Hydrovac Operator Competency and Equipment Training –Workers should be competent in excavation techniques and machinery safety techniques. Hydrovac equipment should only be operated by qualified individuals in accordance with operating manuals provided by the manufacturer.

  • Confined Space – Workers should be knowledgeable about the proper procedures that should be used when working in confined spaces. These spaces may include excavated trenches or the hydrovac tank. All confined spaces should be evaluated by personnel before entry.

  • First Aid – Even when following the best safety practices, accidents can happen. Should such an event occur, it is worthwhile to have someone present on the site who knows how to assess the situation and act appropriately in case of an emergency.

4. Be Wary of Overhead Wires

While hydrovac deals with excavating the ground surface, proper safety practices should be adhered to when working near overhead lines. This is particularly important when the boom movement is in the vicinity of electrical lines.

Safe movement distances should be monitored during equipment set up, while the boom is in use, and when the equipment is being repositioned. When the voltage of the lines is unknown, personnel and equipment should keep a clear distance from overhead lines in accordance with local or regional standards and regulations.

Rival Hydrovac’s trucks, for example, offer as an option, boom sensors that allow for smart positioning of the boom away from overhead electrical lines and other potentially hazardous obstructions.

Hydrovac truck

5. Use the Right Pressure

Hydrovac excavations are considered to be low impact since this technique does not require mechanical cutting tools. However, if water pressures are too high, they can possess enough power to rupture or cut through underground cables.

While the actual recommended pressure depends on several site-related factors, water pressures of around 2000 psi are sufficient for most applications.

Final Thoughts

While hydrovac is relatively safer than other trenching/open-cut methods, they still present several risks to on-site personnel and the general public.

Some of the most pertinent risks associated with hydrovac operations include:

  • Damage to pipeline coatings if hydro excavating at too high of pressures.
  • Impacting water on exposed or already damaged electrical lines.
  • Operating the boom too close to overhead electrical facilities.
  • Not having a shutoff for the pressurized water source in the event of losing control of the water lance.

All of these potential safety risks can be mitigated by assessing site conditions, identifying the potential risks, and implementing a comprehensive HSE plan prior to commencing your HVAC project.