Presentation: Why Are We Still Talking About I/I? – Answers From Statewide Studies by George Kurz
George Kurz emphasizes that infiltration and inflow (I&I) is the most widespread issue in municipal sewer systems, surpassing other concerns such as root intrusion and pre-treatment failures. A major challenge is the lack of reliable methods to quantify I&I, unlike water leakage measurement in water systems. Kurz introduces a spreadsheet-based tool that enables operators to measure I&I using existing monthly operating reports (MORs) without requiring a licensed engineer.
Using Brentwood, Tennessee as a case study, he illustrates how excess water leads to sanitary sewer overflows (SSOs), backups, and treatment inefficiencies by causing flow fluctuations and diluting organic loads. He challenges the notion of simply expanding treatment capacity, citing a Tennessee study that demonstrates its ineffectiveness. Instead, he highlights the rising costs of chemicals and energy and the long-term damage to infrastructure. His statewide study in Tennessee reveals that nearly half of the total sewer flow consists of clear water, not wastewater, with I&I levels increasing 1% annually.
Kurz critiques the Clean Water Needs Survey, pointing out discrepancies between self-reported data and his measured findings. He stresses that the success of I&I reduction projects should be evaluated through before-and-after measurement studies rather than the amount of pipe replaced. His analysis in Brentwood showed a 63% reduction in annual I&I and a 46% decrease in rainfall-dependent I&I after rehabilitation.
Despite challenges in accessing MOR data, Kurz manually processed 170,000 data points to compile his statewide study. He advocates for leveraging this existing data over voluntary surveys to gain a more accurate understanding of I&I. While he acknowledges modern AI solutions, he remains skeptical, favoring measurable, practical approaches. Ultimately, Kurz underscores the need for consistent measurement methods, targeted rehabilitation strategies, and a data-driven approach to effectively manage I&I in municipal sewer systems.
Bio
George E. Kurz, P.E., DEE, Consulting Engineer & Researcher, Sewer Capacity Management
George has 46 years of experience as a government and private engineering consultant focused on improving effectiveness and efficiency in municipal sewer systems. He believes that I/I is the most significant problem facing most operators, but that the true magnitude of the problem is underestimated and has been largely overlooked. He is a specialist in detecting, measuring, and stopping I/I in sewage collection systems. George developed standard methods for measuring effectiveness of rehabilitation using flow monitoring and existing treatment plant data.
