Hydro Excavation in Chicago: Digging Safely Near Utilities

When a utility line is close to where you need to dig, a backhoe is the wrong tool for the last stretch. That is the problem hydro excavation solves. This page explains what it is, what the law says about digging near marked lines, and what to ask before you hire it. It sits inside our excavation and foundation guide.

What is hydro excavation?

Hydro excavation, also called vacuum excavation, uses pressurized water to loosen soil and a vacuum hose to pull the loosened soil into a tank. The crew opens a small hole, sometimes called a pothole, to expose a buried pipe or cable so they can see it instead of guessing. Because nothing hard scrapes the line, the risk of striking it drops.

We are describing the general method here. The specifics, such as water temperature, pressure and truck size, vary by contractor and are not something a City or state rule sets for homeowners.

What does Illinois law say about digging near utility lines?

The Illinois Underground Utility Facilities Damage Prevention Act requires excavators doing non-emergency work to give notice not less than 2 days and not more than 10 days before starting, pre-mark the area, and use hand or vacuum excavation within the tolerance zone (220 ILCS 50). The statute was amended in 2025, so confirm the current text if your job depends on it.

Two things follow. First, near a marked line, the statute names hand or vacuum digging, not machine digging. Hydro excavation is a vacuum method, so it is one way to meet that expectation; ask your contractor which method they use and why. Second, we are not quoting a tolerance zone distance, because it is not in the sources we verified. Read the statute or ask 811 Chicago rather than guessing.

Does hydro excavation replace the 811 call?

No. The call comes first. In Chicago that means 811 Chicago (DIGGER), a free CDOT service, with at least two business days of notice, excluding weekends and holidays, at 312-744-7000 or through the online ticket system (City of Chicago). JULIE covers the rest of Illinois, not Chicago (220 ILCS 50). The call applies to homeowners too (City of Chicago).

The utilities mark their lines, and then the careful digging starts. Check your ticket against the marks first; our guide to reading your DIGGER ticket shows what to confirm. If a crew skips these steps, see how Chicago dig jobs go wrong.

When is hydro excavation worth asking about?

• Utility marks run close to the spot where you need to dig.
• You are digging along a foundation wall that has a service line near it.
• The marks do not match what you see, and you need to confirm where a line really runs.
• The ground is tight, and a machine cannot work near the line.

It is not for every dig. A fence post far from any marks does not need it. Cost depends on the site and the contractor, so ask for a scope, not a guess.

What should you ask a contractor?

1. Do you own the equipment, or do you bring in a subcontractor for it?
2. How will you confirm the marks before the first cut?
3. Who pulls the 811 ticket, and can I have the number?
4. Where does the water and spoil go?

Planning a dig near lines on your property? Our excavation team can walk the site and tell you the safest way to open it.

Common questions

This article explains general rules and common situations in Chicago. It is not legal advice, and City rules change. For a specific property, check with the Chicago Department of Buildings or a licensed professional.