Once it has been treated, wastewater from the Annacis Wastewater treatment plant is released into the Fraser River through an outfall pipe. A new outfall location and diffuser system is being installed, which will involve constructing a one-kilometre long tunnel (approximately) from the plant to the river.
The new outfall location and design will ensure that treated effluent is spread out over a broad area underwater to maximize dilution and minimize the impact on the environment.
Once this new pipe is complete it is expected to meet the regional growth needs for the next 100 years while ensuring greater seismic resilience and continuous, reliable and safe management of liquid waste.
The new outfall pipe will be excavated using a tunnel-boring machine. This machine will be launched from the entry shaft near the Annacis Island wastewater treatment plant and progress south to the river riser in the Fraser River (see illustration below).
The diffuser system will be made up of one long pipe just under the surface of the river bed that will run parallel to the shore. The diffuser system will release treated water through multiple valves attached to the pipe.
The image below shows the diffuser system that will be built in the river bed, parallel to the shore to avoid the river navigation channel.