Hydro & Vacuum Excavation

Hydro-excavation (hydrovac) and air-vac trucks dig by loosening soil with pressurized water or air and sucking it into a tank. It’s the safest way to expose buried utilities, but it has its own hazards.

• Construction
• Utilities
• Oil & Gas

When to use it

• Potholing (daylighting): exposing utilities in the tolerance zone to confirm their exact location and depth before machine digging or boring. See Directional Drilling.
• Digging around congested utilities in streets and plants
• Pole holes, sign footings and slot trenches
• Frozen ground (with heated water)
• Cleaning out catch basins, vaults and pits

Air excavation uses compressed air instead of water. It leaves dry spoil that can be reused as backfill and has less risk of water damage to utilities, but it’s louder, dustier and slower in hard clay.

Hazards

• High-pressure water injection: the wand can cut skin and inject water and dirt into the body. This is a medical emergency even if the wound looks small.
• Damage to utilities from too much pressure or a metal-tipped nozzle held too close
• Suction hose hazards: never put hands or feet near the hose inlet
• Raised debris tank and dump door, and the truck backing
• Noise, slippery mud, and holes left open
• Electrical contact if the hose or boom contacts overhead lines

Safe practices

• Use the pressure and nozzle recommended for digging near utilities. Keep the wand moving and at a safe distance from the line.
• Wear face shield, safety glasses, hearing protection, waterproof gear and boots with metatarsal or toe protection as required.
• Use the dead-man trigger on the wand; never tie it open.
• Barricade or cover potholes when unattended.
• Dump debris only at approved locations.
• Follow the utility owner’s limits on water pressure, nozzle type and water temperature when digging near their lines. Many require a rotating or fan nozzle and limit pressure near plastic gas lines and fiber.
• Keep the nozzle at least the recommended distance from the line, and never point the wand directly at a utility.
• Look up before raising the boom, and keep it away from overhead lines.
• Use a spotter when backing and when positioning the boom over the hole.

Before you start

• 811 ticket valid and marks visible
• Wand, trigger, hoses and fittings inspected; no worn or damaged hose
• Pressure and temperature set for the job and the utility type
• Boom, debris tank, rear door locks and hydraulic lines in good shape
• Traffic control and barricades set
• Two-person crew: one on the wand, one on the suction tube

The debris tank

Never enter the debris tank without following confined space procedures: lockout, ventilation, air testing and a permit if required. When dumping, keep everyone clear of the rear door and the area behind the truck, and never stand under a raised tank. See Confined Spaces.

Last updated: October 1, 2026