Inverted Siphon Condition Assessment and Rehabilitation at Irvine Ranch Water District

Inverted siphons pose unique challenges in maintaining sewer systems. Designed to transport wastewater below rivers, creeks, channels, and other low-elevation obstacles, they are difficult to access for cleaning, inspection, and repair. They also tend to collect sediment and grease. Unfortunately, inadequate maintenance can have expensive consequences. The Irvine Ranch Water District (IRWD), which provides sewer service to Irvine, CA and surrounding communities, has developed a time- and cost-saving condition assessment and rehabilitation approach to addressing wear and tear in four inverted siphons.

Typical planned maintenance of inverted siphons is broken into clear-cut components: cleaning, dewatering, condition assessment, repair recommendations, and finally a construction contract for repair work. Because IRWD has many of these complicated sites, four of these inverted siphons were rolled into one larger construction project bid out in March 2020.

The construction contract includes siphon cleaning and CCTV, CIPP lining of siphon barrels (total of 12 barrels ranging in diameter from 15” to 42”), site access improvements, siphon vault rehabilitation improvements, air jumper repairs, air jumper construction, construction of a chemical dosing facility, two grit traps, and two odor control vents. Throughout the construction phase, the design team identified key decision points. Inspection occurred after cleaning and dewatering, and damaged barrels were rehabilitated as they were identified.

Using the IRWD project as a case study, presenters will provide a real-life example describing which components were inspected during the “engineering phase” and which were inspected during the construction phase to reinforce cost and time savings. Presenters will draw comparisons between this project and more traditional infrastructure rehab programs.

Not all components of a wastewater collection system are created equal. While inverted siphons are only a small fraction of the overall system, they shouldn’t be treated as such. Adequate maintenance improves long-term functionality and viability of this complex infrastructure. Adopting an alternative approach to performing this costly and time-consuming work allows utilities to lower risk while saving time and money.