SEI to SRI Intertie Project

Sewer system maintenance is essential to ensuring reliable service to the City’s ratepayers, to prevent flooding of the built environment, and so maintenance crews can safely access pipes and sewer system structures. Providing operational flexibility to the sewer system also allows the system to be operated in the most efficient manner to ensure reliable service. 

The existing SRO8 combined sewer outfall pipe was built in 1914 and is concrete partially lined with brick. An inspection in 2017 found damage inside the outfall pipe. Part of this project is to rehabilitate the outfall pipe by inserting a smaller diameter polyvinyl chloride (PVC) pipe inside and grouting it in place, providing the outfall pipe a more rigid structure and safer conditions for maintenance and inspection activities of the pipe. 

The second component of this project is to construct a new section of pipe and appurtenances (an intertie) to connect two existing large sewer mainlines (interceptors), the Southend Interceptor to the Snohomish River Interceptor. Both these interceptors convey untreated sewer flows to the Everett Water Pollution Control Facility to be treated. This new intertie will allow the diversion of sewer flow in the Southend Interceptor into the Snohomish River Interceptor, granting better maintenance, repair, and inspection capability of the City’s sewer system.