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New Castle County using soundwaves to examine sewer lines

Katie Peikes
Delaware Public Media
An employee from JMT - the engineering firm that worked with the county on the SL-RAT, demonstrates how it works.

New Castle County will soon deploy a technology that uses sound waves to detect if a sewer line is clean or dirty. County officials demonstrated the technology in Bear Thursday morning.




A Sewer Line Rapid Assessment Tool, or SL-RAT, is acoustic technology that emits soundwaves from one point of a sewer line to another. New Castle County Operations Services Manager Robert Roff said the county has been testing it for a year. They place a transmitter on a manhole and a receiver on another one nearby.


“The transmitter talks to the receiver and it sends soundwaves from one point to the other,” Roff said. “If there are obstructions in the sewer it will slow those soundwaves down.”


The SL-RAT scores the sewer line from zero to 10. A zero means the sewer line is totally blocked while a 10 means it’s completely clear.


New Castle County has over 1,700 miles of sewer lines. County Executive Matt Meyer said he hopes the tech can make it easier for the county to detect blockages or decide which lines need cleaning. 


“It’s very important, obviously, that we detect exactly between which manholes there’s a specific problem so we can address those problems,” he said. 

Credit Katie Peikes / Delaware Public Media
Delaware Public Media
The acoustic technology is placed over a manhole. It sends sound waves through the sewer line to detect whether the sewer is clogged or clean.


Meyer said not all residents realize some of the everyday cooking items they dump down the drains can block the county pipes.


“The public should also know please don’t pour your fat, your oil, your grease down the drain,” Meyer said. “It does have an impact and does ultimately cost you, and all of us in your sewer bills.”


Environmental Compliance Manager Mike Harris said pouring fats, oils and greases down the drain accounts for more than half of the county’s blockages.


“If we keep that out of the system, the sewer doesn’t overflow and doesn’t release into peoples’ basements or into the environment,” Harris said.


New Castle County recently completed the testing phase of the equipment, using it to check on 50,000 feet of pipe so far in the last few months. Officials will deploy it across the county this month. 

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