The technology and use of hydro excavation, also known as vacuum excavation, has been a vital service in the construction industry for many years. It has helped avoid countless accidents and injuries when exposing underground utilities.
Utilities have been placed underground in America for more than 200 years. These underground utilities can include sewer and water laterals, telephone, fuel, and fiber optics. Unfortunately, with many updates and new development to our infrastructure through the years, there can be poor documentation—or sometimes none at all—of abandoned utilities left underground. This can sometimes make it difficult for a contractor to avoid hitting a utility line when excavating, even when diggers hotline has been out to stake with their locating flags.
Hydro excavation can be a more efficient and safer way to expose underground utilities. Hydro excavation liquefies the soil with pressurized water. A large vacuum then sucks the slurry-like mixture into a debris tank, typically mounted on the back of the truck or trailer.
Additional benefits of hydro excavation include:
Utilities that are shallower in the ground, like communication and electrical lines, tend to be more vulnerable. Water laterals in the cold regions of the country run below the frost line. Here in Wisconsin, I prefer running water service at six feet below the ground, especially if it is under a parking lot. I’ve seen frost as deep as five feet in these types of locations. Sanitary sewer laterals can vary in elevation.
Uncovering a utility line that was installed using directional boring can be very difficult without using hydro excavation, even when the utility has been located. Typically, a contractor will dig down alongside the flag, out about three to four feet. The excavator will then slowly and carefully dig into the side toward the utility, exposing it from the side. The excavator learns to read the soil, and when they get into the over dig from when the utility was installed originally, they know they are close to the utility line. Cautiously, the excavator knows to slowly hand dig until the utility is exposed. However, when a utility is installed using directional boring, there is no over dig to give warning that the utility line is near. Hydro excavation can be a great option in these situations.
It is standard practice to call a free locating service (e.g., Diggers Hotline here in Wisconsin) prior to digging. These services, which locate publicly owned underground utilities, typically need 24 hours of notice before excavation or digging begins. A call by the contractor to relocate utilities on the same property may be necessary if the locating flags are lost or after seven days of the first locate. It is critical to know the color codes of the flags to identify the utility located. Check out this helpful chart to learn more about what each color means.
Common projects that need underground locating include planting trees, building decks, installing mailboxes or fences, digging ponds, and pouring concrete.
Diggers Hotline and other free locating services do not locate private underground utilities. Contractors need to do additional research on the property for any unknown obstructions.