The toll tunnel to Sydney's northern beaches is set to cost $1 billion per kilometre

The NSW government’s plan to build a 14-kilometre tunnel connecting Sydney’s inner west to the northern beaches could cost as much as $14 billion – nearly as much as WestConnex at more than twice the length, according to leaked documents.

Fairfax Media has seen confidential documents prepared for cabinet on the project, which adds another $8 billion to the bill for maintenance and operational costs for the tollway over 35 years.

Premier Gladys Berejiklian announced plans for the tunnel in March, saying the tollway would relieve congestion on the northern beaches and cut travel times from the area to the CBD by up to 40 minutes. The proposed Beaches Link tunnel between Seaforth and Rozelle connects with the $17 billion 33km WestConnex tollway currently under construction. When it was first announced, WestConnex was priced at $10 billion.

Yesterday, Fairfax revealed that cabinet documents show the location of six tunnel exhaust stacks , with some just 200 metres from schools. As with the WestConnex project, where the location of exhaust stacks has caused similar concerns, the current proposal has the stacks releasing unfiltered exhaust emissions.

The $14 billion cost includes $5 billion for “contingencies and cost escalation” alongside a $5 construction costs, $2.3 billion in indirect costs and $340 million for property acquisitions, with an estimated 70 properties, including multi-million-dollar homes in leafy north shore suburbs such as Artarmon, Cammeray, Balgowlah and Seaforth on the potential chopping block.

Fairfax Media has more here.

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