What is potholing?
Potholing is digging a small test hole to expose an underground utility so you can confirm its exact location, depth, size and material. Utility locators mark the approximate location on the surface, but marks can be off, and they do not tell you depth. A pothole gives you the real answer before power equipment gets close.
How vacuum excavation works
A vacuum excavation truck loosens soil with high-pressure air or water and vacuums it into a debris tank through a large hose. The result is a clean, narrow hole with little damage to the utility, the pavement or the surrounding ground.
Air vs. hydro excavation
Air excavation uses compressed air to break up soil. The dry spoils can often be used for backfill, and there is no water to haul. It is slower in hard or clay soils.
Hydro excavation uses pressurized water. It cuts faster through hard, compacted or frozen ground, but it creates slurry that has to be hauled off and disposed of properly.
When you should pothole
- Before horizontal directional drilling or boring, to verify crossings.
- Before trenching or setting poles and anchors near marked facilities.
- During design, to confirm depths and avoid conflicts before construction.
- In congested areas with gas, water, fiber and electric lines close together.
- Anywhere a utility strike would be dangerous or costly, such as near gas or high-voltage lines.
What the 811 rules require
Every excavation starts with an 811 call. In California, Arizona and Nevada, you must notify the one-call center at least two working days before you dig, not counting the day you call.
California defines a tolerance zone of 24 inches on each side of the operator’s field marking. Inside the tolerance zone, marked facilities must be located by hand before power equipment is used. Vacuum excavation can be used to locate marked facilities, but you need the facility operator’s permission and must tell 811 you plan to use vacuum excavation when you request your ticket.
Note: Rules change and vary by state and operator. Always confirm current requirements with your one-call center (USA North 811, DigAlert, Arizona 811) and the facility operator before you dig.
More than potholing
The same vacuum equipment is used to pump contaminated water out of vaults and manholes, clean out structures, and pressure wash underground facilities before inspection or work. See our erosion control, stormwater and vault dewatering guide.
Why it pays for itself
A utility strike can mean injuries, outage repairs, fines, project delays and liability. A few potholes cost far less than one damaged gas line or primary cable, and verified depths let your designers and crews plan bores and trenches with confidence.