Sewer Collapse Leads to Extensive Emergency Repair of 2,000 ft of Large Diameter Sewers

On July 16th, 2023, a 20-ft deep, 42-in. reinforced concrete sanitary interceptor sewer collapsed adjacent to a six-lane state highway within an urbanized area of the City of Omaha (City). The sewer collapse created an unstable soil condition resulting in a cave in, jeopardizing the state highway and several utilities. While developing an emergency repair plan for the collapse, the City inspected the surrounding sewers and identified significant deterioration of the infrastructure. As a result, the emergency repair expanded to include nearly 2,000 linear feet of cured-in-place pipe (CIPP) lining of adjacent interceptors ranging in size from 36 in. to 60 in. in diameter. To facilitate the repair work, temporary bypass pumping systems were installed to convey sanitary flows around the planned repairs. This included bypass system setups at 42-in. [10.8 million gallons per day (mgd) capacity], 36-in. (7.2 mgd capacity), and 18-in. (0.70 mgd capacity) interceptor sewers. The bypass force mains had to traverse a recreational trail, under a bridge, and through several private properties. This paper will review the sewer failure, the City’s expedited efforts to stabilize the site, and the emergency repair plan implemented to restore the City’s interceptor system.