Cleveland: Robots guide sewer work

CLEVELAND, Tenn. — A robot camera beams its lights through the darkness and picks up an odd silhouette and transmits it to a monitor where an operator manipulates the little vehicle for a better look.

No, it’s not the latest planetary rover from NASA.

The camera is making its way through an 8-inch-wide sewer pipe below a Cleveland street. The clay pipe under Ramsey Drive has been underground for decades. There are cracks and invading roots where groundwater can seep in and become a burden to the city wastewater treatment system.

The pipe could be dug out of the ground before it collapses, an expensive project that would disrupt traffic for months.

Instead Cleveland Utilities contracted with Alabama-based American Infrastructure Technologies Corp. to install what amounts to an impervious pipe within the pipe.

“We are trying to eliminate extraneous water — stormwater — from the treatment system because we don’t want to treat that,” said Phillip Luce of Cleveland Utilities’ Water and Wastewater Division.

While some cities, including Chattanooga, have used the technology before, this is Cleveland’s biggest such project to date, he said, costing the utility about $400,000.

“We’ve done a lot of work and spent a lot of money the past few years on the problem,” Mr. Luce said. “But it’s something you have to do all the time.”

Jeff Pempeit, the project leader for the contractor, explained how it works.

The robot camera goes through the line, from one manhole to the next, making sure the line is clear and showing where the service lines from houses along the street join the pipe under the street. Images from the camera are transmitted to video monitors inside a truck where an operator is watching.

Then a refrigerated truck backs into place, and the crew feeds a sleeve under air pressure into the manhole and along the line to the next manhole. The sleeve is a polyurethane felt tube saturated with resin. It is cooled in the truck so it doesn’t harden before it gets into the sewer line.

It pops out the next manhole with a loud bang from the air pressure.

Then heat will cure the sleeve in place, hardening into an impregnable pipe within a pipe that will last for decades.

The final step is sending the robot back in, this time with a remote-controlled saw and router that cut out the spots where the house service lines join the pipe.

“We can do in 10 hours what a crew would otherwise do in weeks,” Mr. Pempeit said.

American Infrastructure Technologies is working at several sites here, including the main project on Wildwood Avenue where work is usually done at night on the heavily traveled street.

The work usually attracts some curiosity, he said, wanting to know why the trucks are parked in the street.

“When they find out the alternative, they are usually OK with this,” he said.