Title: Design and Construction Challenges, 96-inch North Secondary Effluent Conveyance The Metro Water Services Central Water Reclamation Facility includes two flow trains that move treated effluent to the plant UV disinfection facility. As a result of major plant expansion work, it was discovered that the northern train could not handle the expected flow due to a previously unidentified restriction in the effluent channel from the grid of clarifiers draining to the channel and ultimately to the North Secondary Effluent Conveyance (NSEC) and the UV Disinfection Facility. After consideration of alternatives B&C and MWS personnel determined that a bypass around the restriction was the feasible alternative to improve the flow characteristics of the NSEC. LDA was selected to provide engineering services to design a 96-inch diameter bypass around the restriction to divert flow from the effluent channel upstream of the restriction to connect to the existing 108-inch NSEC. The project consisted of cutting two openings in the existing effluent channel, construction of a new 18’X19’X22’ deep Junction Structure (designed by Barge Design), 420’ of 96” spiral wound steel pipe, and connection of the 96” steel pipe to the existing 108” concrete NSEC via a 108”X96” steel wye. The major design challenge was developing the methodology for connecting a new spiral wound steel pipe to the existing reinforced concrete pipe. The design had to consider the structural capabilities of the RCP, subgrade conditions, and particularly creating a permanent seal between it and the new steel pipe. After design and permitting were finalized Cleary Construction was selected to construct the project. Due to the importance of the NSEC and the treatment facilities draining to it during high flows, a tight window of construction was made available for the work to be carried out. The window was established based on historic rainfall and plant flow records. Construction challenges were numerous: • Construction of the junction structure in close proximity to an existing clarifier and the effluent channel • Excavation for the 108-inch by 96-inch wye installation required support of numerous existing utilities and safety concerns relative to the wide, deep excavation in soils that were previously disturbed during plant facility construction • Construction of the complicated connection scenario laid out in the design • Window for shut down of the NSEC conveyance to make the connections at the effluent channel and existing pipe Key Takeaways: Without any standard design criteria for connecting the 108-inch concrete and 96-inch steel pipes, consideration for pipe support, end to end connections, and maybe most important, creating a seal between the two materials were all critical to a successful project. A tight construction window, potential subgrade issues, numerous existing utilities at the tie-in point, deep excavations, and other construction considerations were carefully considered, plans and backup plans were developed, and experienced construction team members were assigned to the project. The team assembled for the project and Metro Water Services personnel worked closely together to accomplish a critical outcome at the Central Water Reclamation Facility.