The Joint Water Pollution Control Plant Effluent Outfall Tunnel Project will replace the two existing effluent outfall tunnels with one 18-foot diameter, 7-mile long tunnel. The proposed tunnel will handle current and future flows while providing seismic resistance and system redundancy. The purpose of the project is to protect local waterways by addressing infrastructure, providing seismic redundancy meeting current standards and eliminating overflow concerns during large storm events. The main construction components of the project include a connection to the existing Secondary Effluent Pump Station Force Main, a 14-foot diameter conveyance structure, the shaft for the 18-foot ID tunnel, an 18-foot minimum diameter tunnel and the proposed Manifold Structures.
Sequoia is providing comprehensive quality control inspection and materials testing services to the General Contractor, Dragados. The scope of services includes inspection and testing for the construction of 7-mile long 18-foot diameter tunnel, which includes the prestressed tunnel liner, concrete tunnel and appurtenant structures.