Excavation
Hydro-Excavation and Potholing (Vacuum Digging)
Cojo
July 9, 2026
6 min read
Hydro excavation is a non-destructive digging method that uses pressurized water to break up soil and a powerful vacuum to suck up the slurry, leaving buried utilities exposed and unharmed. It is the safest way to dig around gas, power, water, and fiber lines, and it is the standard method for potholing -- digging small test holes to confirm exactly where a utility sits before other work starts. On Oregon jobsites with congested underground and expensive-to-hit lines, vacuum excavation prevents strikes that mechanical digging can cause. This guide explains how it works and when it pays off.
A hydro excavation truck carries a water tank, a high-pressure pump, and a large vacuum with a debris tank. An operator directs a focused stream of water into the ground to cut and liquefy the soil, then the vacuum lifts the slurry up a hose into the tank. There is no digging blade near the utility -- water does the cutting, and water will not slice through a pipe or cable the way a bucket tooth or shovel can.
The result is a clean, precise hole exactly where you want it, with the utility exposed and intact. When the work is done, the hole can be backfilled and the slurry hauled off or disposed of properly.
Oregon requires you to call 811 before you dig so utilities get located and marked. But locate marks show an approximate path, not an exact depth or position. Digging with a machine inside that tolerance zone risks a strike. Hydro excavation solves that:
A utility strike is dangerous and expensive -- a hit gas line is a life-safety event, and cutting fiber or power can trigger big repair and outage costs. Vacuum excavation is cheap insurance against all of that. The master excavation guide covers how this fits into safe site work.
Potholing utilities means digging small, targeted holes to verify where lines run before committing to a design or a dig. Typical Oregon uses include:
Potholing pairs naturally with trench boring under a driveway, where crews expose the utilities on each side before boring between them.
Vacuum excavation is a specialty tool, not a replacement for bulk earthmoving. You would not dig a basement with it. You use it precisely where safety or accuracy matters most, then let conventional excavation handle the volume. A stabilized construction entrance and rock pad often supports the same jobsite where hydro potholing is happening.
Water-based digging behaves differently depending on what is in the ground, and Oregon offers plenty of variety. In Willamette Valley clay, the pressurized water cuts well but the spoil comes up as heavy, sticky slurry that fills the debris tank fast and is slower to haul. Sandy coastal soil vacuums easily and cleanly, which is one reason vacuum excavation is a favorite near the coast. Central Oregon can be the hard case -- basalt and cemented layers resist water cutting, so hydro excavation is used to strip soil down to rock and expose a utility rather than to dig through the rock itself.
Hot-water hydro units matter in Oregon winters, since a heated stream cuts frozen crust that a cold jet would only glaze. Matching the truck and water setup to the season and the soil keeps the dig moving.
Hydro excavation is usually priced by the hour or by the pothole, and it runs higher per hour than a standard excavator because the equipment and operator are specialized.
| Item | Baseline Range |
|---|---|
| Hydro excavation truck + operator, hourly | $200 -- $500+ per hour |
| Potholing, per hole (daylighting a utility) | $150 -- $600+ per hole |
| Excavator + operator, hourly (for comparison) | $150 -- $350+ per hour |
| Disposal of slurry / spoil, per load | $75 -- $300+ per load |
| Mobilization fee | $250 -- $800+ flat |
The cost of potholing is almost always far less than the cost of a utility strike, which is why it is standard practice on congested sites.
The spoil from hydro excavation comes up as a wet slurry, and it has to go somewhere legal. It cannot simply be dumped -- it is hauled off in the debris tank and disposed of at an approved site, which is part of why the method is priced higher than dry digging. On a tidy jobsite the exposed hole is backfilled and compacted, or the utility is left daylighted for the survey or the next crew, then the surface is restored.
Oregon's wet season is actually a decent time for vacuum work compared to mechanical digging, because there is no open trench sitting in the rain and the disturbed footprint stays small. Still, 811 locates apply year-round, and pumped or spilled water on site should be kept out of storm drains just like any other discharge. Because the method leaves such a small scar, it is often the right call in finished landscaping, near mature trees, or on paved areas where a full open cut would mean expensive restoration.
Hydro excavation is the tool you reach for when hitting a buried line is not an option. Non-destructive, precise, and safe around utilities, it protects crews, infrastructure, and budgets. Cojo is a CCB licensed and insured Oregon excavation contractor, Hood River based and serving statewide, and we coordinate safe digging around marked utilities. See our excavation services or request a free estimate.
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