The leaked documents in 2017 put the cost of building the two motorway tunnels at $14 billion, almost as much as the 33-kilometre WestConnex toll road project.
The seven-kilometre Beaches Link will extend from the Warringah Freeway at Cammeray to Balgowlah and Seaforth in the city’s north-east, burrowing as deep as 108 metres. The tunnels will be three lanes in both directions.
New documents seen by the Herald indicate construction of the Beaches Link will begin in 2023. Work is likely to be carried out between 7am and 6pm on Monday to Friday and 8am to 1pm on Saturdays.
Tunnelling beneath Cammeray will vary between 18 metres and almost 50 metres, while reaching depths of more than 100 metres below Northbridge.
The government is justifying the multi-billion dollar spend by highlighting the reduction in road congestion and subsequent travel-time savings for motorists.
It will allow drivers to bypass 19 sets of traffic lights through The Spit, Mosman and Neutral Bay, cutting travel times by more than 30 minutes between Balgowlah and CBD.
While the state budget made no mention of the Beaches Link, the government has said that development money was allocated for it as part of the Western Harbour Tunnel project.
Mr Constance said the project would also integrate with new and existing public transport, including more than five kilometres of cycle and pedestrian pathways.
“There will be the opportunity for new express bus services to key centres including St Leonards, Macquarie Park, North Sydney and Sydney CBD, and direct access to North Sydney to interchange with the new Sydney Metro,” he said.
The government said last year that 35 homes would be acquired for the Beaches Link, the vast majority of which are next to Balgowlah Golf Course. The state also intended to buy a further 13 “non-residential properties” for the project.
Parts of the Warringah Freeway, used by as many as 250,000 vehicles a day, will be temporarily shut overnight during the construction of the Western Harbour Tunnel and subsequent upgrades to the adjoining motorway.
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Tom Rabe is Transport Reporter with The Sydney Morning Herald.
Matt O’Sullivan is City Editor at The Sydney Morning Herald.