SL RAT in operation

Oakland, Maine Acoustic Sewer Inspection Program Nets $51,000 Savings

Located in rural Maine, the Town of Oakland sets an example for how small towns can efficiently manage their collection system. Incorporated in 1883, Oakland sits in the heart of the Belgrade Lakes region.

The Town municipal collection system has approximately 11.6 miles of gravity sewer and the system is comprised of 52 percent PVC pipe, with the remainder including a mix of clay, transite, and fiberglass pipe. Oakland services 800, mostly residential locations. Historically, the Town could only budget annually for one mile of cleaning and CCTV inspection — at best — based on its limited resources. Since the Town doesn’t own its equipment, officials must hire out all work, at great expense. This lack of resources combined with significant ongoing maintenance needs has made it especially critical that they focus and prioritize their efforts.

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Like many small, rural towns, the issues the Town of Oakland faced were not just due to a lack of resources but how efficiently those resources were being deployed. Understanding this challenge, Oakland officials turned to new technology. Specifically, Oakland used acoustic inspection to screen its system rapidly and economically for blockages and anomalies. This information has helped optimize the Town’s resource allocations and better direct its cleaning equipment to the right pipe at the right time.

GIS map

The Science of Acoustic Sewer Inspection Technology

Acoustic inspection is a fast, low-cost, and low-resolution method to inspect small-diameter gravity sewer lines. The Sewer Line Rapid Assessment Tool, or SL-RAT, manufactured by InfoSense, is designed to help utilities quickly screen its small-diameter gravity sewer lines to prioritize specific pipes that need cleaning or more detailed inspection.

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The SL-RAT technology has been commercially available since 2012. Its two components work together by “yelling” down the pipe between two adjacent manholes and “listening” for how the known signal has been degraded by anomalies that degrade flow capacity. Depending on the unique pattern of how much sound energy passes through, the SL-RAT assigns the pipe segment a score ranging from 0 to 10. A zero indicates a completely obstructed pipe, and a 10 indicates a pipe segment with significant additional capacity for flow. The device requires no flow contact or confined space entry, allowing a two-person crew to consistently measure over 10,000 ft per day.

As InfoSense CEO Alex Churchill says, “By first screening your system with the SL-RAT, you can identify and prioritize the correct pipes in your system that need attention rather than wasting resources just blindly cleaning area by area. This efficiency improvement can have a massive impact.”

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SL RAT in manhole illustration

Rapid Success and Impactful Savings

Oakland started its acoustic sewer inspection program with a short-term SL-RAT project in 2021. Given the Town’s small size, a crew of two inspected its entire gravity sewer collection in only a few weeks. The data was uploaded to the InfoSense Sewer Line Data OrGanizer or SL-DOG where it was archived and exported for analysis. Any pipe segments that scored poorly were flagged for cleaning. After initial success with the technology, the town completed another SL-RAT project that reassessed their system again in 2022.

The acoustic data served as a force multiplier, magnifying the impact of the Town’s existing cleaning and CCTV work, highlighting how technology can help drive efficiency and offset resource limitations. Out of its entire system, only a small percentage — 15 percent — required follow-up action. After taking follow-up measurements one year later, town management was able to identify the root causes of underlying pipe defects — such as root growth — that had caused segments to become rapidly clogged — even after a recent cleaning.

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SL DOG Portal

According to municipal engineer and SL-RAT program manager Boyd Snowden, “The SL-RAT serves two purposes in Oakland: assessing which pipes are currently blocked and identifying underlying issues in our system. Using the SL-RAT, we have reduced both cleaning costs and SSO risks in our system saving us significant time and money.”

By first screening with accounts, the program saved more than $51,000, while reducing the risk of sanitary sewer maintenance issues, sanitary sewer overflows and customer backups. The program also helped Oakland meet its insurance due diligence requirements. The use of acoustic sewer inspection technology has provided the Town with a reliable, rapid, low-cost method to assess its current collection system and provides peace of mind that needed maintenance issues can be economically identified and addressed proactively.

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Chase Mendell is a marketing strategist at InfoSense Inc.

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