Vacuum excavation, such as hydro excavation, is a growing technology used to prevent jobsite damages throughout the world. This non-mechanical method of excavation continues to grow in use due to its proven success in preventing costly – and sometimes catastrophic –
damage to underground utilities.
Vacuum excavation is a combination of two non-mechanical sources to excavate. The first source is pressurized water or air used to loosen and break up the soil. Once the soil is loosened, the second non-mechanical source – vacuum and airflow – removes material from the excavation and stores it in a debris body or hopper. The material is contained in the debris body to be transported offsite for disposal, loaded into another transportation vehicle, or even dumped onsite and used as backfill. Because vacuum excavation is non-mechanical, the potential to damage an underground utility such as gas lines, fiber optics, or electrical lines is significantly reduced.
Many states have established excavation best practices stating a tolerance zone around a utility. The tolerance zone is a defined distance on each side of the underground utility where only hand tools or vacuum excavation can be employed. The size or width of the tolerance zone can vary by state. With hand tools, the assumption is the excavation work is being performed slowly and gently like an archaeologist on a dig site. But digging by hand with a shovel can be very damaging to buried utilities.
Common Ground Alliance DIRT Report
The Common Ground Alliance (CGA) – a utility industry association committed to saving lives and preventing damage to underground infrastructure by promoting effective damage prevention practices – tracks and publishes the Damage Information Reporting Tool (DIRT) Report every year on underground damages, facility type, and their cause. The CGA’s most recent report from 2015 showed there were 288,346 known reported events of underground
facility damage in North America – that is one damage incident every two minutes! And these are only known incidents. The actual number of incidents is likely much higher.
The CGA also tracks excavation method employed. According to the 2015 CGA report, 40% of underground damage was caused by backhoes and trenchers, which are used more frequently for excavation.
The report also indicates that 26% of underground damage was caused by hand tools, making hand tools the second leading cause of known underground damage. This is somewhat troubling when you consider that the hand tools that caused this damage were used within the established tolerance zone.
Conversely, according to the CGA report, vacuum excavation accounted for less than 0.2% of underground damage. Employing vacuum excavation instead of hand tools could reduce almost 75,000 known incidents of underground
damage each year.
While vacuum excavation accounted for 234 reported incidents of underground damage in 2015, many of these incidents could have been prevented. It is likely these incidents were due to improper use of the vacuum excavation equipment.
TSSA, GTI Best Practices
At Vactor Manufacturing, we refer to the Technical Standards and Safety Authority (TSSA) of Ontario’s Guideline for Excavation in the Vicinity of Utility Lines and the Gas Technology Institute’s (GTI) hydro excavation best practice and guidelines for recommended operating techniques and pressure for vacuum excavators. Headquartered in
Toronto, the TSSA is a not-for-profit, self-funded organization dedicated to enhancing public safety. An independent technology organization based in Illinois, GTI addresses issues impacting the natural gas and energy markets.
TSSA and GTI both recommend the following best practices for the non-destructive use of vacuum excavators:
• Do not exceed 3,000 psi when using a spinning or rotating nozzle.
• Do not exceed 2,500 psi when using a straight jet nozzle.
• Do not exceed 1,500 psi when excavating 18 inches or more below surface.
• Always keep the digging lance moving to avoid concentrating the pressurized air or water on a single point.
• Maintain eight inches between the end of the pressure wand and the underground facility.
• Never heat water above 115° F.
• Always be properly trained on the equipment and its safe operation.
Additional best practices:
• Never use more than 3,000 psi of water pressure when hydro excavating. Excessive water pressure can damage underground utilities.
• Use equipment designed for the application.
• Only use digging lances or vacuum tubes featuring protective non-conductive coatings.
Keeping Equipment in Top Condition
Vacuum excavation equipment maintenance best practices are as important as operating best practices. As with any piece of mechanical equipment, maintenance is extremely important. Vacuum excavation equipment works in some of the toughest and dirtiest conditions. There are three essential maintenance recommendations: always clean the unit at the end of the day; always inspect the unit for wear or broken components that need to be replaced; and always follow the manufacturer’s recommendations for oil changes and the greasing of moving components.
With a hydro excavation truck, there is a water tank and water pump that must be periodically maintained; cleaning or replacing filters and water pump oils.
Routine greasing of bushing and bearing surfaces will prevent premature wear and failure. Furthermore, maintaining a proper oil change and filter replacement schedule will keep the blower and hydraulic system clean and long lasting.
Service and maintenance timetables vary by component. Vactor provides a comprehensive hourly guide with all our operating manuals. Additionally, all lube points are clearly labeled with recommended maintenance intervals. There are also daily items to inspect and clean such as the blower filtration system (filter and cyclone).
Hoses and safety equipment should be inspected prior to the start of every day. This inspection is critical to ensuring safer and more efficient operation. Many hydro excavation contractors have included this inspection as part of their DOT pre-trip inspection.
The filtration system and vacuum hose are the primary check points. The filters should be cleaned daily to ensure proper protection of the blower system. The vacuum hose sees the most abuse during the vacuum excavation operation, so these components should be reviewed for integrity daily.
Any abuse on the filtration system will allow material to carry over through the blower, which reduces blower performance. Changing the filters per the manufacturer’s recommendations is key to a long-lasting vacuum excavator.
Handguns and water lances should also be inspected to ensure they are in safe working order.
Proper and safe operation of vacuum excavation equipment is the main priority for most manufacturers. Training in the areas of proper setup,
operation, excavation techniques and load handling helps to ensure that the operator is familiar with the specific method of vacuum excavation so they can safely maximize their efficiency and productivity on the job.
Many manufacturers, including Vactor, provide training designed to provide the customer with an overview of the equipment, training on proper and safe operation of the equipment and application, and to provide maintenance overview and frequency.
Following vacuum excavation best practices and providing proper operator training not only helps reduce incidents of underground damage, it also helps lower the cost of equipment operation, improve business efficiency, increase productivity on the job, and ensure longer equipment life.
Ben Schmitt is the product manager for Vactor’s entire vacuum excavation product line. Schmitt has held roles in engineering, sales and, most recently, product management. He can be reached via email at: email@example.com.