Acciona’s section includes the northern end of the tunnel project, including the approximately 1-mile crossing under the harbor itself. Major work on Stage 2 is slated to start later this year and last about five years.

Stage 2 of the Western Harbour Tunnel project includes boring the northern end of the tunnel and fit-out of the full tunnel.
Image courtesy of New South Wales Government

The designers say they will deliver a design that avoids dredging for an immersed tube tunnel as had originally been planned by instead using tunnel boring machines. They aim to minimize any impacts on the marine environment, as well as any disruption to commercial and recreational harbor users.

“The improved design and construction method is an excellent example of industry collaboration and is expected to deliver significant reductions to the amount of steel and concrete required, as well as other environmental benefits, compared to the original reference design,” Richard Barrett, head of AECOM’s Australia and New Zealand business, said in a statement.

Using the two TBMs will eliminate the need for two planned surface construction sites and for temporary cofferdams, according to NSW officials.

Tunneling for the 1.1-mile Stage 1 segment, led by John Holland CPB Contractors, began last June. The work includes excavation but no tunnel fit-out, which will be included in Stage 2. Stage 1 work is expected to continue through next year and into 2024.