The Department of Public Works of Rockville, Maryland, has always been open to high-tech help. The city’s sewer inspection force has recently adopted the Sewer Line-Rapid Assessment Tool, better known as the SL-RAT, by InfoSense, and significantly reduced flushing costs. 

The compact device is operated by a two-person crew and relies on acoustic technology to rapidly assess blockages in a length of sewer pipe between two manholes. 

The SL-RAT consists of a transmitter — which sends an acoustic signal down the pipe — and a receiver, which estimates the available air space above the sewer flow. A reading of zero indicates that a pipe is completely blocked, while a reading of 10 indicates it’s completely open.

The equipment is designed to work optimally in sewer pipes between 6 and 12 inches in diameter to a maximum length of 800 feet. Once manhole covers are removed, readings can be completed in as little as five minutes with no confined space entry. 

“Initially, some of our crew members were a little skeptical of working with the equipment,” says James D. Woods, an engineer with the department. “They’d tested out the unit on various types of pipes and noticed that the readings didn’t appear consistent. However, the way the SL-RAT works is by comparing results from the same type of pipe and looking for anomalies across a series of readings.” 

Once workers in the field warmed up to the technology and inspections began to produce results, the department assigned a two-person crew to work with the SL-RAT full time, up to four days per week.

At the current rate, the entire system will be acoustically inspected inside of two years. 

“Before we used the SL-RAT we tended to flush all of the pipes as we were inspecting them, as part of routine maintenance,” Woods says. “We now only flush the pipes when we know there’s an obstruction inside them. That’s cut our flushing budget significantly and allowed us to concentrate on flushing the worst spots and flushing them more frequently.

"We’re finding smaller pipe blockages before they flare up, and ultimately this is resulting in fewer mainline stoppages.”

Increasing in population density, Rockville is paving the way for growth by repairing, rehabbing and replacing its pipe infrastructure at an aggressive pace, while establishing a reputation for investing public funds to producd tangible results.