Vacuum excavation services
What is vacuum excavation?
Also known as non-destructive digging (NDD) or soft digging, vacuum excavation is a safe method commonly employed to assist in identifying valuable underground utility infrastructure when potholing.
How does hydro vacuum excavation work?
The vacuum excavation process utilises powerful air suction to remove loose materials and convey them to a holding tank. Where materials are hard-packed and bound together, a high-pressure water lance is used to break up and loosen materials around the target area. Once broken into smaller pieces, suction can be reapplied to remove the loose materials. These materials are held in a holding/spoils tank and can be removed from the work area and taken to a suitable waste disposal location, stockpiled on site, or reused to backfill the same location at the completion of vacuum excavation works.
Benefits of using a hydro vacuum excavator
- Safe alternative to mechanical excavation
Safety is paramount when conducting all works. With more and more services now being installed or rerouted in the ever-expanding underground utility network, vacuum excavation provides a safe option compared to mechanical excavators, whose powerful and sharp implements can strike underground pipes and cable assets.
- Potholing of assets
Where telecommunication, power, gas, water and sewer assets have been electronically located and surface paint marked, vacuum excavation provides a simple and unique method of direct keyhole excavation to the asset for physical identification.
- Able to get into hard-to-reach places
Even hand digging can have its limitations when working around congested areas. A vacuum hose is flexible and allows access to those hard-to-reach spots. Hose extensions and accessories can be added to achieve the desired results for each application exposing underground utility services.
- Contains spoils and waste in a sealed tank environment
Hazardous materials are captured in a sealed holding tank, which allows for controlled disposal. What happens to ground materials when foreign materials have been introduced is unknown, and this can lead to personnel being exposed to possible dangers such as broken glass, syringes, chemicals, asbestos and sharp metal fragments.
- Exposing utility assets in congested places
Where assets are located in congested areas, vacuum excavation is ideal for safely working around and exposing existing services without causing any damage.
- Pit cleaning for safe access
Utility service pits provide access to pipes, valves, cables, solenoids, service meters and expansion loops, but are exposed to weather and surrounding environmental elements. The pits are not completely sealed and usually have keyholes for pit seal breaker lifting tools. Soil, leaves and other materials can build up inside the pits, and they quite often become homes for many friendly and not-so-friendly spiders, wasps, snakes and other species. Vacuum cleaning is an excellent method of creating a clean and safer environment before personnel access the pits.
- Very low dust levels
Vacuum excavation machines are fitted with filtering systems to greatly reduce airborne material. Most vacuum units run with 10-micron filters. Any dust that may be created is usually from using the water lance to break up soil materials prior to vacuuming.
- Reduced risk of asset damage
A great advantage of vacuum excavation is being able to minimise the possible risk of asset damage, which could occur when using other mechanical excavation methods. When services and equipment have to remain energised, vacuuming becomes a very valuable safe work method.
- Less destructive to surrounding environment
Vacuum excavation avoids disturbing surrounding features and minimises large earthwork excavations where possible by focusing on very specific areas.
- Utility asset identification and verification of depth, size and type
Where underground utilities have been electronically located, vacuum potholing is used to remove a small amount of subsurface material so physical identification can be made of the depth, size and material type of the service. A PVC tube is placed in the hole on top of the services as a marker, and all utility service attributes are labelled on the tube for future reference.
- Utility Line locating
Identify existing asset services and physically follow the service to verify any changes or anomalies not previously known.
- Faster compared to hand digging
Vacuum extraction is a very fast and efficient method. Loose sand is quickly removed, and where harder materials such as clay are encountered, high-pressure water is utilised to break up the material prior to vacuuming. Hand digging can lead to high fatigue and injury from constant bending and moving heavy loads.
- Access areas where conventional excavation machines are not practical
Many locations within existing buildings, under bridges and power lines, or in closed-in areas can have limited access for mechanical machinery. Vacuum excavating provides an excellent alternative for accessing those locations.
- Construction assistance e.g. fence posts, light posts, traffic lights, sign posts, trench footings.
Using vacuum excavation for fencing construction has major advantages for post or pole installation, as boundary fencing and underground services can run in close proximity to each other. Vacuum excavation provides a very safe method compared to mechanical augering. If any underground Telstra services, water pipes or power cables have not been identified by electronic detection, the vacuum will expose the service, which is far better than cutting or breaking a service and exposing personnel to possible dangers or expensive company repair costs.
- Engineering inspection assessments
Various engineering inspections require physical identification. Vacuum excavation allows a very small area to be removed without disturbing the surrounding structure. The keyhole created can be used to insert a video inspection camera.
- Vacuum instead of hand auger
Some drilling companies are required to hand auger the first metre as an extra measure to avoid any underground services. A useful alternative is a vacuum excavation pothole prior to drilling, excavating a hole and inserting a PVC sleeve. The sleeve also assists the crew by working as a marker for all holes to be drilled.
- Re-level
Foundations, footings, tanks and concrete slabs may require removal of surplus support material to obtain the desired RL. Vacuum excavation provides excellent advantages, as existing structures do not have to be removed.
- Anchor points
Vacuum excavators are high-powered suction machines and can be applied to different engineering tooling applications. The power of suction can act as an anchor point for equipment machine bases.
Hydro vacuum excavators come in various sizes depending on the required task, but they share the same basic mechanical process. Below are a few of the main mechanical components and their basic functions:
- Hose – the flexible hose conveys the materials
- Tank – the spoils tank holds the captured materials
- Filtration – cyclonic separator and fine filters remove small particles
- Blower pump – positive displacement blowers pump large volumes of air with powerful suction
- Motor – drives the blower and accessories
- Water pressure pump – provides high-pressure water to the lance for material break-up
Duty of Care
It is important to understand “duty of care” when working near underground utility services. Asset owners working to AS5488-2013 Quality Level A (QL-A) require positive validation of underground services, and this can only be done by potholing by hand or using non-destructive digging (vacuum excavation).