Construction of Perth’s $2.8 billion Alkimos Seawater Desalination Plant has reached a major milestone, with more than 6km of undersea tunnelling completed as a dry winter underlines the need for a new source of drinking water.
The separate intake and outfall tunnels, extending 2.5km and 4km respectively, have been bored beneath the seabed off Alkimos in Perth’s northern suburbs.
The intake tunnel will draw seawater into the plant, while the outfall tunnel will return concentrated brine to the ocean. Together, they are the longest desalination intake and outfall tunnels in Australia.
Tunnel-boring machines named Mary and Karli spent 15 months excavating as much as 50 metres a day, up to 20 metres beneath the seabed. About 32,000 concrete segments made in Western Australia were installed to line the tunnels.
The tunnelling follows the installation of the offshore intake and outfall structures by Beverley, Australia’s largest registered jack-up barge. Marine exclusion zones around the work sites have now been removed, although vessels will continue to carry out inspections, surveys and commissioning checks.
Water Corporation said the project would now move towards connecting the tunnels to the offshore structures, while work continues on the plant’s buildings, mechanical systems and electrical infrastructure across the 29-hectare site.
Stage one is designed to produce 50 billion litres of drinking water each year, enough to supply more than 2.5 million people and reduce pressure on groundwater sources affected by declining rainfall.
The project is expected to support more than 1,500 local jobs and remains on track to begin producing water in 2028. Water Minister Daniel Pastorelli said the recent dry winter made it more important for residents to use water carefully, despite desalination becoming a central part of Perth’s future supply.
