The two scoping reports also show one of the options under consideration for the underground crossing of Sydney Harbour is an"immersed tube tunnel"sitting on top,or within the top layers,of softer sediments on the bottom of the harbour. The two other options involve digging twin tunnels to deeper depths below the harbour.
The cost oflinking Balgowlah in the city's north to Rozelle in the inner west have been estimated in leaked cabinet documents at $14 billion and from motorists paying tolls on northbound journeys of the Sydney Harbour Bridge and Harbour Tunnel.
The scoping reports show the state government has fielded more than 1000 comments from the public about the location and operation of ventilation stacks for the proposed tunnels. About 650 comments from the community related to the design of the project,such as tunnel entries and exits,526 to public transport alternatives and 501 to potential property impacts such as compulsory acquisitions.
The reports do not reveal where ventilation stacks will be located,other than say that they are"being developed as part of the project design".
But Fairfax Media has previously revealed the that were contained in a series of leaked cabinet documents. The six planned exhaust stacks are between 20 metres and 35 metres high and,including Wenona and Anzac Park Public.
The latest reports also fail to provide more specific details about properties affected across the entire project. When to the new toll road in March,about 71 property owners were identified as being affected by preliminary work on the Beaches Link.
The 14-kilometre tunnel project is likely to be split into two separate but co-ordinated construction packages:the Western Harbour Tunnel and an upgrade to the Warringah Freeway,and the Beaches Link and connection to the Gore Hill Freeway.
Transport planners considered five potential corridors for the Beaches Link before naming a preferred"more southerly alignment"that passed under Northbridge and crossed under Middle Harbour near Seaforth Bluff.
The southerly corridor was viewed as having"better road network connectivity",shorter tunnels with flatter gradients,and"reduced environmental impacts"compared with the others.
The report on the Beaches Link and a connection to the Gore Hill Freeway spruiks the travel time saved by motorists who will be able to bypass 19 sets of traffic lights for a trip between Balgowlah and North Sydney. It will allow motorists to avoid – for the price of a toll – the congested Military and Spit roads,and the Spit Bridge.
"There is currently poor connectivity between the Northern Beaches and wider metropolitan area,characterised by long and unreliable road and public transport journey times,"the reports said.
One of the biggest construction challenges will be upgrading the Warringah Freeway – one of Australia's busiest roadways – and building connections to the Beaches Link and new harbour tunnel.
"Construction of the Warringah Freeway upgrade component would require detailed construction staging and extensive out-of-hours works to minimise substantial traffic impacts,"the reports said.
About from the Warringah Freeway each weekday,and traffic can grind to a halt when accidents or breakdowns occur.
Apart from reconfiguring the freeway from near Milsons Point to Naremburn,local roads in North Sydney and Cammeray will be need to be upgraded and changes made to on and off ramps.
Up to five of the road and pedestrian bridges across the freeway may also require"adjustment,replacement or relocation". They include the High Street road bridge and the Ridge Street pedestrian bridge.
An indicative timetable for construction of the harbour tunnel and an upgrade of the Warringah Freeway is for it to start in 2019 and be completed by 2025.
That will mean the new harbour tunnel will be finished two years after the final stage of WestConnex,which it will connect to at an
Roads and Maritime Services prepared the scoping reports to consider potential environmental issues,and likely impacts for further investigation.