Enhancing Regional Collection System Resilience through Collection System Mortality Projections

Many gravity collection systems installed in the 1970’s and earlier, particularly those composed of vitrified clay pipe, are entering a period of rapidly accelerating pipe failures, getting closer to the end of their expected service life with rapidly escalating costs and increasing risk of system failures. Seven special purpose Districts and three Cities used pipe life expectancy curves as a cost-effective “first-step” towards projecting near-term and long-term asset management needs and developing resilient renewal strategies. The goal is to achieve and sustain timely system renewal and resilience through measures that restore the full structural integrity of the sewer, achieved either by full replacement or CIPP lining of the gravity sewer main and a fraction of the associated sewer manholes and laterals. The findings of this study inform each District/City on their individual requirements to ‘catch-up’ with deferred system renewal needs and define consistent, long-term levels of annual renewal.