Assessing Rehabilitation Techniques Through Hydraulic Modeling

Purpose Collection system modeling is traditionally completed to assess network condition, achieve infiltration and inflow (I/I) removal, evaluate alternatives, and to develop source reduction programs (SRPs). Eight SRPs were developed for the Kline's Island Sewer System (KISS) to assess the impact of different I/I elimination strategies, and each was incorporated into a scenario of the hydrological/hydraulic model by adjusting the contributing runoff surface values and base infiltration accordingly. I/I reductions were derived from a compendium of rehabilitation effectiveness studies and performance metrics collected over the last 20 years that classified a diverse range of rehabilitation techniques (nearly 30) by effectiveness reduction percentage for the four contributing runoff surfaces. Benefits of Presentation This is a novel method for modeling the impacts of manhole, main, tap, riser, lateral, and private-side sewer rehabilitation techniques. This presentation is relevant to programs that use modeling to assess impact of rehabilitation techniques on sewer baseline infiltration and peak wet weather flows. This method allows for countless rehabilitation strategies to be applied to a model and further evaluated, especially if meaningful assessment of the underlying flow data are also conducted to identify the most effective technique to apply on a catchment by catchment basis. This provides insight on how to develop a catchment-tailored SRP that optimizes cost and I/I reduction, including the ability to differentiate between inflow and rainfall induced infiltration, thereby reducing capital expansion projects. Status of Completion The project team successfully used this modeling method to create eight unique SRPs, utilizing various types and amounts of rehabilitation techniques. These were applied to over 40 modeled alternatives followed by costing exercises to quantify the capital, operating, and replacement life cycle cost of each alternative with the respective SRP applied. The final alternatives provided options that leveraged the benefits of rehabilitation in order to eliminate nine large capital expansion projects. Conclusion The final alternatives provided options that leveraged the benefits of rehabilitation in order to eliminate nine large capital expansion projects.