Crews use 'vacuum truck' to unclog sewers, locate utility lines

J. Michael Ross
City employee Dale White starts the sewer cleaning processes.

Dale White and Doug Gaston are two of the “nearly invisible” people who work for the city's Public Works Department. Along with their supervisor, Director Nick Williams, they constantly work to improve the quality of life.

They operate the city’s “vacuum truck,” an ingenious contraption that helps unclog sewers and makes finding buried utilities easier, less labor intensive and best of all, safer.

They are part of a large group whose jobs are to make sure that services such as police, medical emergency, fire and all facets of public works are up to muster, readily available and accessible to the public.

“This truck was originally designed to be a sewer truck to clean out the sewers. The jet that runs the front hose shoots water at 3,000 psi [pounds per square inch] right down inside the sewer line and the only thing pulling that hose is the force of the water,” White explains.

“So you run the line down into the line and when you find an obstruction, you cut your pressure back to between 800 and 1,200 psi so you don’t flood everybody out. At that point that water is cutting roots, grease, anything that could be in there.

“The newer parts of the sewer system that are PVC we don’t have to run nearly as much; it’s generally the older clay tile lines that have problems.”

So that explains the basics of sewer maintenance, but what about the safety and buried utility lines?

White says, “More and more the utilities that are going in are being buried underground. Anytime you have buried electric, buried gas, it’s a hazard. If there’s a leak or other problem, you have to have the utility company come out and locate the lines and hope their marks are accurate.”

And this is where the vacuum truck shines: “They’ve adapted this truck to do what they call ‘hydro-excavating' now - digging with water. This is new for the city and it’s been a learning curve for us as far as how much you can use the equipment without tearing it up.”

In a nutshell, the crew simultaneously sprays water at high pressure on a concentrated point on the ground above where the buried utility line is supposed to be. At the same time a large vacuum arm and tube sucks the displaced soil into a tank on the truck for later disposal at the waste water treatment plant.

The process of hydro-excavation thus eliminates the traditional – and potentially dangerous - process of digging blind with a backhoe or shovels to physically locate the lines. [This process is shown in the accompanying photo.]

“So unless it’s solid rock, we can get to it without tearing up any gas or electrical lines and get the crew to what they’re looking for without any accidents. We can just expose what they’re looking for with the water.

“It means they can physically see the line rather than just some yellow paint on the ground where the line is supposed to be. It helps them out a bunch.”

And being there to help us all out a bunch – and thus improving the quality of our lives - is exactly what the “nearly invisible” crew of the vacuum truck and the rest of the folks in all of the city services are there to do.