Des Moines WRA Rehabilitates 78″ Reinforced Concrete Trunk Sewer Using Spincast Methods

In 2016, the Des Moines Water Reclamation Authority (WRA) authorized a system-wide assessment of their pre-2004 constructed trunk sewers, which included nearly 60 mi of gravity and force main pipelines. From this initial assessment, approximately 20% of the inspected sewers were identified as high-risk and programmed for rehabilitation. The Phase 2 sewer lining included approximately 3,600 ft of 78-in. diameter reinforced concrete pipe (RCP) and associated structures. The original sewer was constructed in the 1960s and had experienced notable thickness loss from the concrete pipe wall caused by the presence of hydrogen sulfide within the sewer. Up to 3 in. of wall loss was measured in some areas, with the first layer of reinforcement being partially or completely exposed. The goal of the project was to restore the structural integrity of the original sewer and protect it from future deterioration. The Phase 2 project was located in downtown Des Moines, Iowa, beginning just north of MLK Parkway and extending south, terminating at the Raccoon River. One unique element of this project included sections of sewer located within an EPA Superfund, further limiting cost-effective options to repair the original sewer. Ultimately, trenchless spincast rehabilitation was selected to avoid excavation throughout the project. A cementitious mortar with an anti-microbial additive was applied to the pipe wall to achieve the project goals. Other notable project elements included the cleaning and disposing of large amounts of debris deposited at the bottom of the large-diameter sewer and an innovative approach to bypass. Lining continued through the Summer, Fall, and Winter of 2022 and was completed in the Spring of 2023.