Sewer Pipe Failures

Environmental and structural factors have long been known to impact the longevity of a sewer pipe’s service life. Many Wastewater operators rely on their years of on-the-job experience to decide which lines are most at risk for failure. In a recent study by experts from the Civil Environmental and Geodetic Engineering department at The Ohio State University, researchers conducted statistical analyses to investigate the most common factors in concrete sewer line failure and collapse.

Cities often have tens of thousands of miles of sewer pipes running beneath them. And, because they are underground, spotting issues is not as simple as finding issues with above-ground infrastructure like roads or power lines, said Soroush Zamanian, a graduate research associate in civil, environmental, and geodetic engineering at Ohio State and lead author of the paper. Cracks that impact structural integrity can be the first signs that a sewer pipe is compromised and potentially on its way to collapse. One of the biggest problems for many cities around the world, these sewer systems have been installed long ago, and the challenge now is to maintain these old systems.

“In 2017, the American Society of Civil Engineers gave the United States’ overall sewer system a D+ rating,” explained Soroush Zamanian, one of the report’s authors, to Ohio State News. “And that’s part of why we are looking at this question and seeing if we could help predict where lines might fail.”

Evaluating the Causes of Pipe Failure

To run the study, the researchers gathered and analyzed data from underground concrete pipes in the United States. They investigated 16 common causes of sewer pipe failure, including the density and makeup of surrounding soil, the elasticity and strength of the concrete materials and the weight of ground-level vehicular traffic that passed over different lines. After running various statistical analyses, they determined that two of these factors were most likely to lead to pipe cracking and failure: weak concrete (either made of poor materials or poorly maintained) and the weight of trucks that drove over them on a regular basis.

Utilizing the Findings for a Better Future

This study presented clear insight into the varying factors that contribute to the longevity of a sewer pipe’s service life. “The big picture is if we want to design sewer pipes for the future, or if we want to assess the current condition and predict future conditions of these pipes, one key element is to know the important factors contributing to their failures – and how do those factors play out in the real world,” Zamanian said. Many operators maintain hundreds or thousands of miles of pipe, and knowing which lines are likely to fail sooner can help them prioritize and schedule regular inspections to ensure structural integrity is maintained, and to catch existing problems before they become crises. In addition, these findings can help installers improve outcomes for future pipes by selecting stronger, longer-lasting materials or placing pipes in locations that don’t experience heavy truck traffic.

Any information can be helpful when it comes to maintaining a sewer system. From inspection data collected by CCTV, or risk factors already known to the operators. All of this adds up to board picture of system-wide conditions allowing crews to work most efficiently.

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