What is Hydro Excavation and its Benefits?
Hydro excavation, or sometimes called hydro vac excavation, is a non-destructive digging process that uses high pressure water guns or hydro jetters to cut through soil and by vacuum (vac) transfer soil into a vacuum tank truck.
This method dramatically reduces the risk associated by trenching and excavation using a metal backhoe bucket and augers around buried utilities, cables, pipelines and underground infrastructure.
Hydro excavation is far faster than hand digging and safer than hydraulic metal attachments to expose underground infrastructure. Certain regions only permit vacuum excavators around gas lines and fiber optic lines.
A vacuum excavation truck can be configured to reach the work site as far as 400 feet from truck, or to work in deep pits or in rocky soils. The soil or water suction hose is typically 6 or 8 inches in diameter and rocks that are larger than the hose can be lifted and placed aside – the vacuum is sometimes strong enough to lift a 100 pound rock.
There are trade-offs when using a 6 or 8 inch diameter tube. A 6 inch tube requires 3,000 cubic feet per minute to carry debris into its tank and for the same performance in a 8 inch diameter tube, 5500 of cubic feet per minute of air is needed. Because of the additional horsepower, more fuel is used, increasing operating cost – therefore, specifying the correct hydro excavator is crucial for profitable operations.
Benefits of hydro vac excavation:
- Reduces static electricity
- Works in a variety of soil conditions
- Water works as a lubricant
- Eliminates the sandblasting effect
- Heated water excavates frozen ground
Benefits of air vacuum excavation:
- Faster cleanup time
- Backfill material is dry
- Water tanks are not needed
- Efficiently loosens soil
Hydro vac excavation is gaining industry attention for its high productivity and efficiency. Hydro excavators can dig 30 holes in a day. Typical digging operations are reduced due to the surgical precision of the excavation and reduction in soil rehabilitation.
Examples of efficiencies:
- 410 ft long trench, 5 inches wide, 3 feet deep done in 9 hours
- 29 feet long, 18 inches wide, 3 feet deep done in 1 hour
Daylighting (or Potholing) and Pole Holes
- 45 hydro excavation hole 22 in diameter, 8 feet deep, completed in eight hours
- 8 feet deep, 22 inch diameter, through clay, completed in 20 minutes
- 8 feet deep, 22 inch diameter, through soft clay, completed in 15 minutes
- 5 Utility poles, 7 feet deep, 20 inch diameter, through sandy clay, 175 feet away from truck, 7 hours
- 55 Test holes, 4 feet deep, 10 hours
Trenches can be as narrow as 3 inches and up to 30 feet deep and can reach 400 feet away from the truck.
Unlike hydro vacuum excavators, a sewer jetter operates at 3,000 to 4,000 PSI which could easily damage underground utilities, and so variable water pressure control at less than of 2,000 PSI is safer when digging trenches using water pressure. Hydro vac excavation at an improper water pressure increases the chance of damaging line covers or casings as well as injuring operators.
Excessive supply gallons per minute of water during hydro vac excavation increases debris dumping, thereby reducing cost-effectiveness and loss of time.
Frozen ground can be surgically cut through, thanks to high temperature water that is heated in pump cabinets and a boiler.
The system should have specially designed tools to make hydro vac safe – for instance, making sure that the water suction hose end that lifts the debris is covered on neoprene and the jetter hose end is coated with rubber ensures that neither have sharp metal edges that could dent, nick or cut through pipes or cables.
Vacuum truck manufacturers now offer both high pressure water and compressed air to hydro vac excavation contractors – so they have options for digging and loosening different soil conditions.
Hydro excavation trucks can be used for:
- Debris removal and general cleanups
- Slot trenching and excavating
- Directional drilling test holes
- Potholing or Daylighting
- Service and splice pits
- Pipeline and utility crossings
- Waterline repair
- Sign and pole installation
- Valve box cleaning
- Storm Drains
- Public Works
- Road Construction
- Utility Engineering
- Power Plants
- Commercial Construction
- Municipal Utilities
- Electrical Utilities
Hydro excavation is gaining recognition as best practices for exposing underground utilities in frozen and or congested grounds. Governments are enacting laws that will drive contractors to use hydro excavation as a best practice method to prevent damage to underground infrastructure.